Implants for spinal fixation and or fusion

ABSTRACT

Bone implants, including methods of use and assembly. The bone implants, which are optionally composite implants, generally include a distal anchoring region and a growth region that is proximal to the distal anchoring region. The distal anchoring region can have one or more distal surface features that adapt the distal anchoring region for anchoring into iliac bone. The growth region can have one or more growth features that adapt the growth region to facilitate at least one of bony on-growth, in-growth, or through-growth. The implants may be positioned along a posterior sacral alar-iliac (“SAI”) trajectory. The implants may be coupled to one or more bone stabilizing constructs, such as rod elements thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/874,149, filed May 14, 2020, which is a continuation of InternationalApplication No. PCT/US2020/018402, filed Feb. 14, 2020, which claimspriority to U.S. application Ser. No. 16/276,430, filed Feb. 14, 2019,U.S. Provisional Application No. 62/859,646, filed Jun. 10, 2019, andU.S. Provisional Application No. 62/933,250, filed Nov. 8, 2019; all ofthe disclosures of which are incorporated by reference herein for allpurposes.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference. For example,this application incorporates by reference in their entireties U.S.Patent Publication No. 2011/0087294, U.S. Patent Publication No.2011/0087296, U.S. Patent Publication No. 2011/0118785, and U.S. PatentPublication No. 2011/0125268.

FIELD

The present disclosure generally relates to bone implants. Morespecifically, the present disclosure relates to bone implants used forthe stabilization, fixation and/or fusion of the sacroiliac joint and/orthe spine.

BACKGROUND

Many types of hardware are available both for the fixation of bones thatare fractured and for the fixation of bones that are to be fused(arthrodesed).

For example, the human hip girdle is made up of three large bones joinedby three relatively immobile joints. One of the bones is called thesacrum and it lies at the bottom of the lumbar spine, where it connectswith the L5 vertebra. The other two bones are commonly called “hipbones” and are technically referred to as the right ilium and-the leftilium. The sacrum connects with both hip bones at the sacroiliac joint(in shorthand, the SI-Joint).

The SI-Joint functions in the transmission of forces from the spine tothe lower extremities, and vice-versa. The SI-Joint has been describedas a pain generator for up to 22% of lower back pain.

To relieve pain generated from the SI-Joint, sacroiliac joint fusion istypically indicated as surgical treatment, e.g., for degenerativesacroiliitis, inflammatory sacroiliitis, iatrogenic instability of thesacroiliac joint, osteitis condensans ilii, or traumatic fracturedislocation of the pelvis. Currently, screws and screws with plates areused for sacroiliac fusion. At the same time the cartilage is generallyremoved from the “synovial joint” portion of the SI-Joint. This requiresa large incision to approach the damaged, subluxed, dislocated,fractured, or degenerative joint.

Additionally, long constructs can be used to join, fuse and/or stabilizea plurality of vertebrae in the thoracic, lumbar, and sacral portions ofthe spine. These long constructs may include one or more rods. Forexample, to treat spinal disorders such as degenerative scoliosis, theL5 vertebra to the S1 vertebrae can be fused using a system of implantsand rods as described herein.

SUMMARY OF THE DISCLOSURE

The disclosure herein generally relates to one or more of bone implants,their methods of use, or their methods of assembly. The implants hereinmay be used in one or both of the treatment of a SI-Joint, or as ananchoring component for a construct that joins, fuses and/or stabilizesvertebrae.

One aspect of the disclosure is an implant for use in at least one ofbone fusion or stabilizing a plurality of bones. The implant includes adistal anchoring region and a growth region that is proximal to thedistal anchoring region, the distal anchoring region having one or moredistal surface features that adapt the distal anchoring region foranchoring into iliac bone, and the growth region includes one or moregrowth features that adapt the growth region to facilitate at least oneof bony on-growth, in-growth, or through-growth.

The implant is optionally a composite implant. A composite implant mayhave an inner elongate member such as a shank and an outer elongatemember such as a sleeve. An inner shank may have a distal end regionwith one or more threads sized and configured for anchoring into iliacbone. An outer sleeve can be sized and configured to be positioned overat least a portion of the inner shank. A sleeve may be positionedrelative to an inner member to form a composite implant with an innermember interface feature and a sleeve interface feature interfacing eachother so as to resist relative motion between the sleeve and the innermember in at least one direction.

A distal anchoring region can have one or more distal surface featuresthat better adapt the distal anchoring region for anchoring into iliacbone than the growth region, and the growth region can have one or moregrowth features that better adapt the growth region to facilitate atleast one of bony on-growth, in-growth, or through-growth than theanchoring region.

An inner member (e.g. an inner shank) may be more resistant to fatiguethan an outer member (e.g. an outer sleeve).

The implants herein are optionally not composite implants.

One aspect of the disclosure herein includes a method of implanting animplant, optionally a composite implant, for use in at least one offusing or stabilizing bony tissue. The method includes advancing theimplant along a posterior sacral alar-iliac (“SAI”) trajectory until adistal anchoring region is disposed in iliac bone and growth region isdisposed across the SI Joint. The method can include coupling a tulip orother coupling member to the implant, and optionally coupling aconstruct member (e.g. rod), to the tulip.

One aspect of the disclosure is a method of assembling a composite boneimplant for use in one or more of fusing or stabilizing bone. The methodincludes positioning an outer member (e.g. sleeve) such that the outermember is disposed over an inner member (e.g. inner shank). Forming thecomposite implant may include forming a composite implant such that aninner member (e.g. shank) interface feature and a sleeve interfacefeature interface each other so as to resist relative motion between thesleeve and the inner member in at least one direction. A compositeimplant may have a distal anchoring region and a growth region that isproximal to the distal anchoring region, the distal anchoring regionoptionally having one or more distal surface features that better adaptthe distal anchoring region for anchoring into iliac bone than thegrowth region, and the growth region optionally having one or moregrowth features that better adapt the growth region to facilitate atleast one of bony on-growth, in-growth, or through-growth than theanchoring region.

One aspect of the disclosure is an inner shank that can be used as partof a composite bone implant. The inner shank can include any of thefeatures described or claimed herein.

One aspect of the disclosure is an outer sleeve that can be used as partof a composite bone implant. The outer sleeve can include any of thefeatures described or claimed herein.

In some merely exemplary embodiments, an implant for use in fusing andor stabilizing a plurality of bones is provided with a shank portion, abody portion and a head portion. The shank portion has a proximal endand a distal end. The body portion is coupled to the shank portion andis configured to be placed through a first bone segment, across a bonejoint or fracture and into a second bone segment. The body portion isconfigured to allow for bony on-growth, ingrowth and through-growth. Thehead portion is coupled to the proximal end of the shank portion and isconfigured to couple the shank portion to a stabilizing rod.

A body portions as used in this context may include any of the sleevesherein.

In some embodiments of the above implants, the distal end of the shankportion is provided with threads for securing the implant to the secondbone segment. In some embodiments, the first bone segment is a sacrumand the second bone segment is an ilium. The body portion may beintegral with the shank portion. The body portion may include at leastone rectilinear face to prevent rotation. In some embodiments, the bodyportion has a cross-section transverse to a longitudinal axis that istriangular in shape to prevent rotation. The body portion may include atleast one apex to prevent rotation. In some embodiments, the bodyportion includes a plurality of fenestrations that each communicate witha central lumen of the body portion. The shank portion may include atleast one spline that mates with a slot within the body portion toprevent relative rotation between the shank portion and the bodyportion.

In some embodiments, an implant for use in fusing and or stabilizing aplurality of bones is provided with a shank portion, a body portion anda head portion. The shank portion has a proximal end and a distal end.The body portion is coupled to the shank portion and is configured to beplaced into a first bone segment. The body portion is configured toallow for bony on-growth, ingrowth and through-growth. The head portionis coupled to the proximal end of the shank portion and is configured tocouple the shank portion to a stabilizing rod.

In some embodiments, the first bone segment is a vertebra, a sacrum oran ilium. The distal end of the shank portion may be provided withthreads for securing the implant to the second bone segment. In someembodiments, the body portion is integral with the shank portion. Insome embodiments, the body portion includes at least one rectilinearface to prevent rotation. The body portion may have a cross-sectiontransverse to a longitudinal axis that is triangular in shape to preventrotation. In some embodiments, the body portion includes at least oneapex to prevent rotation. The body portion may include a plurality offenestrations that each communicate with a central lumen of the bodyportion. In some embodiments, the shank portion includes at least onespline that mates with a slot within the body portion to preventrelative rotation between the shank portion and the body portion. Thedistal end of the shank portion may be provided with a plurality ofbristles to allow the shank portion to be distally inserted into a bonebut inhibit proximal removal from the bone.

One aspect of the disclosure is an implant for use in at least one offusing or stabilizing bony tissue, comprising: an elongate body sizedand configured such that the elongate body can be implanted across asacro-iliac (“SI”) joint and extend into a sacrum and into an ilium(optionally to or beyond a tear-drop shaped region); a distal anchoringregion of the elongate body having one or more distal surface featuresthat are configured to anchor the distal anchoring region to iliac bone,and a proximal region of the elongate body disposed proximal to thedistal region, the proximal region having one or more proximal surfacefeatures adapted to allow at least one of bony on-growth, in-growth, orthrough-growth.

One aspect of this disclosure is a bone stabilizing implant, comprising:an elongate implant body; and one or more deployable members, the one ormore deployable members each having a non-deployed position and adeployed position relative to the elongate implant body. An elongateimplant body can include one or more threads, optionally a plurality ofregions having different number of leads. An elongate implant caninclude a plurality of rows of openings (optionally linear rows), eachof the rows including a plurality of openings separated by a portion ofthe elongate implant body. A portion of the elongate implant body thatseparates the plurality of openings can include one or more threads. Anyof the deployable members can include a plurality of protrusionsextending from a spine, the protrusions extending further radiallyoutward than the spine, and optionally the protrusions formed integrallywith the spine. One or more deployable members can be positionedrelative to the elongate implant body such that they are deployed uponactuation of an internal deployment member. An internal deploymentmember can comprise a plurality of radially protruding camming surfacesthat when rotated cause the one or more deployable members to moveradially outward. One or more threads on an elongate implant body canprovide a mechanical radial stop to one or more deployable members,optionally preventing the opening(s) from bowing under load. Any of theopenings may be tapered to limit play between an elongate implant bodyand one or more deployable members. An elongate implant body can haveone or more lattice sections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of an implant structure.

FIGS. 2A-2D are side section views of the formation of a broached borein bone according to one embodiment of the invention.

FIGS. 2E and 2F illustrate the assembly of a soft tissue protectorsystem for placement over a guide wire.

FIGS. 3 and 4 are, respectively, anterior and posterior anatomic viewsof the human hip girdle comprising the sacrum and the hip bones (theright ilium, and the left ilium), the sacrum being connected with bothhip bones at the sacroiliac joint (in shorthand, the SI-Joint).

FIGS. 5 to 7A and 7B are anatomic views showing, respectively, apre-implanted perspective, implanted perspective, implanted anteriorview, and implanted cranio-caudal section view, the implantation ofthree implant structures for the fixation of the SI-Joint using alateral approach through the ilium, the SI-Joint, and into the sacrum.

FIGS. 8A to 8C illustrate embodiments of an implant structure with ahead portion joined using a Morse taper.

FIG. 9 illustrates an embodiment of an implant structure with a headportion joined using a screw type attachment.

FIGS. 10A and 10B illustrate an embodiment of an implant structure withan integrated head portion.

FIGS. 11A and 11B illustrate embodiments of an implant structuresuitable for pedicle screw salvage.

FIG. 12 illustrates an embodiment of an implant structure with ananchor.

FIGS. 13A and 13B illustrate the attachment of a tulip structure to animplant structure and the securing of a rod to the tulip structure.

FIGS. 14 and 15 illustrate alternative embodiments of head portions withexpandable attachment features.

FIG. 16 illustrates an embodiment of an implant structure with ascrew-like head portion that extends completely through the stem portionof the implant structure.

FIG. 17 illustrates an embodiment of the attachment of the head portionto the stem portion of the implant structure using a ball and socketjoint.

FIGS. 18A to 18E illustrate the head portion of the implant structure inconnection with a tulip structure.

FIGS. 19A and 19B illustrate a lateral view and an axial view of anembodiment of the implant structure crossing the SI-Joint using aposterolateral approach entering from the posterior iliac spine of theilium, angling through the SI-Joint, and terminating in the sacral alae.

FIG. 20A is an anatomic posterior perspective view, exploded prior toimplantation, of a representative configuration of an assembly of one ormore implant structures, sized and configured to achieve translaminarlumbar fusion in a non-invasive manner and without removal of theintervertebral disc.

FIG. 20B is an anatomic inferior transverse plane view showing theassembly shown in FIG. 20A after implantation.

FIG. 21A is an anatomic posterior perspective view, exploded prior toimplantation, of a representative configuration of an assembly of one ormore implant structures, sized and configured to achieve lumbar facetfusion, in a non-invasive manner.

FIG. 21B is an anatomic inferior transverse plane view showing theassembly shown in FIG. 21A after implantation.

FIG. 21C is an anatomic lateral view showing the assembly shown in FIG.21A after implantation.

FIG. 22A is an anatomic posterior view showing, in an exploded viewprior to implantation, another representative configuration of anassembly of one or more implant structures sized and configured toachieve fusion between lumbar vertebra L5 and sacral vertebra S1, in anon-invasive manner and without removal of the intervertebral disc,using a posterolateral approach entering from the posterior iliac spineof the ilium, angling through the SI-Joint, and terminating in thelumbar vertebra L5.

FIG. 22B is an anatomic posterior view showing the assembly shown inFIG. 22A after implantation.

FIG. 23A is an anatomic anterior perspective view showing, in anexploded view prior to implantation, a representative configuration ofan assembly of one or more implant structures, sized and configured tostabilize a spondylolisthesis at the L5/S1 articulation.

FIG. 23B is an anatomic anterior perspective view showing the assemblyshown in FIG. 23A after implantation.

FIG. 23C is an anatomic lateral view showing the assembly shown in FIG.23B.

FIG. 24 is an axial view illustrating an implant inserted through aposteromedial approach.

FIG. 25A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 25B is an exploded view showing the components of the bone implantof FIG. 25A.

FIG. 25C is a side view showing the bone implant of FIG. 25A.

FIG. 25D is a top plan view showing the bone implant of FIG. 25A.

FIG. 25E is a distal end view showing the bone implant of FIG. 25A.

FIG. 25F is a side sectional view schematically showing a portion of thebone implant of FIG. 25A.

FIG. 25G is a side sectional view schematically showing a variation of aportion of the bone implant of FIG. 25A.

FIG. 26A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 26B is an exploded view showing the components of the bone implantof FIG. 26A.

FIG. 26C is a side view showing the bone implant of FIG. 26A.

FIG. 26D is a top plan view showing the bone implant of FIG. 26A.

FIG. 26E is a distal end view showing the bone implant of FIG. 26A.

FIG. 27A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 27B is a side sectional view showing the bone implant of FIG. 27A.

FIG. 28A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 28B is a side sectional view showing the bone implant of FIG. 28A.

FIG. 29A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 29B is a side sectional view showing the bone implant of FIG. 29A.

FIG. 30A is a perspective view showing an exemplary embodiment of a boneimplant having a tulip or coupling device provided at its proximal end.

FIG. 30B is a side sectional view showing the bone implant of FIG. 30A.

FIG. 31 is an example of a composite implant.

FIGS. 32A and 32B illustrate imaging showing an exemplary SAI trajectoryfor implanting a SI Joint stabilization implant across the SI joint,with the arrow indicating the trajectory.

FIG. 33A illustrates an exemplary composite implant.

FIG. 33B illustrates an exemplary elongate inner member.

FIG. 33C illustrates an exemplary outer member.

FIGS. 34A and 34B illustrate an exemplary composite implant.

FIG. 35 illustrate an exemplary inner member.

FIGS. 36A-36C illustrate views of an exemplary composite implant.

FIG. 37 illustrates an exemplary inner member.

FIG. 38 illustrates an exemplary inner member.

FIG. 39 illustrates a portion of an exemplary composite implant.

FIG. 40 illustrates a portion of an exemplary composite implant.

FIGS. 41A and 41B illustrate portions of an exemplary composite implant.

FIG. 42 illustrates a portion of an exemplary composite implant.

FIG. 43 illustrates a portion of an exemplary composite implant.

FIGS. 44A and 44B illustrates views of an exemplary composite implant.

FIG. 44C illustrates an exemplary inner member.

FIGS. 45A and 45B illustrate an exemplary composite implant.

FIGS. 46A-46D illustrates views of an exemplary composite implant.

FIG. 46E illustrates an exemplary inner member.

FIG. 47 illustrates an exemplary composite implant.

FIGS. 48A, 48B, 48C, 48D, 48E, 48F, 48G and 48H illustrate an exemplaryimplant with one or more deployable members.

DETAILED DESCRIPTION

Elongated, stem-like implant structures 20 like that shown in FIG. 1make possible the fixation of the SI-Joint (shown in anterior andposterior views, respectively, in FIGS. 3 and 4) in a minimally invasivemanner. These implant structures 20 can be effectively implanted throughthe use a lateral surgical approach. The procedure is desirably aided byconventional lateral, inlet, and outlet visualization techniques, e.g.,using X-ray image intensifiers such as a C-arms or fluoroscopes toproduce a live image feed, which is displayed on a TV screen.

In one embodiment of a lateral approach (see FIGS. 5, 6, and 7A/B), oneor more implant structures 20 are introduced laterally through theilium, the SI-Joint, and into the sacrum. This path and resultingplacement of the implant structures 20 are best shown in FIGS. 6 and7A/B. In the illustrated embodiment, three implant structures 20 areplaced in this manner. Also in the illustrated embodiment, the implantstructures 20 are rectilinear in cross section and triangular in thiscase, but it should be appreciated that implant structures 20 of otherrectilinear cross sections can be used.

Before undertaking a lateral implantation procedure, the physicianidentifies the SI-Joint segments that are to be fixated or fused(arthrodesed) using, e.g., the Fortin finger test, thigh thrust, FABER,Gaenslen's, compression, distraction, and diagnostic SI-Joint injection.

Aided by lateral, inlet, and outlet C-arm views, and with the patientlying in a prone position, the physician aligns the greater sciaticnotches and then the alae (using lateral visualization) to provide atrue lateral position. A 3 cm incision is made starting aligned with theposterior cortex of the sacral canal, followed by blunt tissueseparation to the ilium. From the lateral view, the guide pin 38 (withsleeve (not shown)) (e.g., a Steinmann Pin) is started resting on theilium at a position inferior to the sacrum end plate and just anteriorto the sacral canal. In the outlet view, the guide pin 38 should beparallel to the sacrum end plate and in the inlet view the guide pin 38should be at a shallow angle anterior (e.g., 15 degrees to 20 degreesoff the floor, as FIG. 7B shows). In a lateral view, the guide pin 38should be posterior to the sacrum anterior wall. In the outlet view, theguide pin 38 should be superior to the first sacral foramen and lateralof mid-line. This corresponds generally to the sequence showndiagrammatically in FIGS. 2A and 2B. A soft tissue protector (not shown)is desirably slipped over the guide pin 38 and firmly against the iliumbefore removing the guide pin sleeve (not shown).

Over the guide pin 38 (and through the soft tissue protector), the pilotbore 42 is drilled in the manner previously described, as isdiagrammatically shown in FIG. 2C. The pilot bore 42 extends through theilium, through the SI-Joint, and into the S1. The drill bit 40 isremoved.

The shaped broach 44 is tapped into the pilot bore 42 over the guide pin38 (and through the soft tissue protector) to create a broached bore 48with the desired profile for the implant structure 20, which, in theillustrated embodiment, is triangular. This generally corresponds to thesequence shown diagrammatically in FIG. 2D. The triangular profile ofthe broached bore 48 is also shown in FIG. 5.

FIGS. 2E and 2F illustrate an embodiment of the assembly of a softtissue protector or dilator or delivery sleeve 200 with a drill sleeve202, a guide pin sleeve 204 and a handle 206. In some embodiments, thedrill sleeve 202 and guide pin sleeve 204 can be inserted within thesoft tissue protector 200 to form a soft tissue protector assembly 210that can slide over the guide pin 208 until bony contact is achieved.The soft tissue protector 200 can be any one of the soft tissueprotectors or dilators or delivery sleeves disclosed herein. In someembodiments, an expandable dilator or delivery sleeve 200 as disclosedherein can be used in place of a conventional soft tissue dilator. Inthe case of the expandable dilator, in some embodiments, the expandabledilator can be slid over the guide pin and then expanded before thedrill sleeve 202 and/or guide pin sleeve 204 are inserted within theexpandable dilator. In other embodiments, insertion of the drill sleeve202 and/or guide pin sleeve 204 within the expandable dilator can beused to expand the expandable dilator.

In some embodiments, a dilator can be used to open a channel though thetissue prior to sliding the soft tissue protector assembly 210 over theguide pin. The dilator(s) can be placed over the guide pin, using forexample a plurality of sequentially larger dilators or using anexpandable dilator. After the channel has been formed through thetissue, the dilator(s) can be removed and the soft tissue protectorassembly can be slid over the guide pin. In some embodiments, theexpandable dilator can serve as a soft tissue protector after beingexpanded. For example, after expansion the drill sleeve and guide pinsleeve can be inserted into the expandable dilator.

As shown in FIGS. 5 and 6, a triangular implant structure 20 can be nowtapped through the soft tissue protector over the guide pin 38 throughthe ilium, across the SI-Joint, and into the sacrum, until the proximalend of the implant structure 20 is flush against the lateral wall of theilium (see also FIGS. 7A and 7B). The guide pin 38 and soft tissueprotector are withdrawn, leaving the implant structure 20 residing inthe broached passageway, flush with the lateral wall of the ilium (seeFIGS. 7A and 7B). In the illustrated embodiment, two additional implantstructures 20 are implanted in this manner, as FIG. 6 best shows. Inother embodiments, the proximal ends of the implant structures 20 areleft proud of the lateral wall of the ilium, such that they extend 1, 2,3 or 4 mm outside of the ilium. This ensures that the implants 20 engagethe hard cortical portion of the ilium rather than just the softercancellous portion, through which they might migrate if there was nostructural support from hard cortical bone. The hard cortical bone canalso bear the loads or forces typically exerted on the bone by theimplant 20.

The implant structures 20 are sized according to the local anatomy. Forthe SI-Joint, representative implant structures 20 can range in size,depending upon the local anatomy, from about 35 mm to about 60 mm inlength, and about a 7 mm inscribed diameter (i.e. a triangle having aheight of about 10.5 mm and a base of about 12 mm). The morphology ofthe local structures can be generally understood by medicalprofessionals using textbooks of human skeletal anatomy along with theirknowledge of the site and its disease or injury. The physician is alsoable to ascertain the dimensions of the implant structure 20 based uponprior analysis of the morphology of the targeted bone using, forexample, plain film x-ray, fluoroscopic x-ray, or MRI or CT scanning.

Using a lateral approach, one or more implant structures 20 can beindividually inserted in a minimally invasive fashion across theSI-Joint, as has been described. Conventional tissue access tools,obturators, cannulas, and/or drills can be used for this purpose.Alternatively, the novel tissue access tools described above and inco-pending U.S. Application No. 61/609,043, titled “TISSUE DILATOR ANDPROTECTOR” and filed Mar. 9, 2012, which is hereby incorporated byreference in its entirety, can also be used. No joint preparation,removal of cartilage, or scraping are required before formation of theinsertion path or insertion of the implant structures 20, so a minimallyinvasive insertion path sized approximately at or about the maximumouter diameter of the implant structures 20 can be formed.

The implant structures 20 can obviate the need for autologous bone graftmaterial, additional pedicle screws and/or rods, hollow modularanchorage screws, cannulated compression screws, threaded cages withinthe joint, or fracture fixation screws. Still, in the physician'sdiscretion, bone graft material and other fixation instrumentation canbe used in combination with the implant structures 20.

In a representative procedure, one to six, or perhaps up to eight,implant structures 20 can be used, depending on the size of the patientand the size of the implant structures 20. After installation, thepatient would be advised to prevent or reduce loading of the SI-Jointwhile fusion occurs. This could be about a six to twelve week period ormore, depending on the health of the patient and his or her adherence topost-op protocol.

The implant structures 20 make possible surgical techniques that areless invasive than traditional open surgery with no extensive softtissue stripping. The lateral approach to the SI-Joint provides astraightforward surgical approach that complements the minimallyinvasive surgical techniques. The profile and design of the implantstructures 20 minimize or reduce rotation and micromotion. Rigid implantstructures 20 made from titanium provide immediate post-op SI-Jointstability. A bony in-growth region 24 comprising a porous plasma spraycoating with irregular surface supports stable bone fixation/fusion. Theimplant structures 20 and surgical approaches make possible theplacement of larger fusion surface areas designed to maximizepost-surgical weight bearing capacity and provide a biomechanicallyrigorous implant designed specifically to stabilize the heavily loadedSI-Joint.

To improve the stability and weight bearing capacity of the implant, theimplant can be inserted across three or more cortical walls. Forexample, after insertion the implant can traverse two cortical walls ofthe ilium and at least one cortical wall of the sacrum. The corticalbone is much denser and stronger than cancellous bone and can betterwithstand the large stresses found in the SI-Joint. By crossing three ormore cortical walls, the implant can spread the load across more loadbearing structures, thereby reducing the amount of load borne by eachstructure. In addition, movement of the implant within the bone afterimplantation is reduced by providing structural support in threelocations around the implant versus two locations.

In some embodiments, the implant structure can function like a pediclescrew to allow fixation and/or fusion of bone such as the spine and/orSI-Joint. For example, long constructs can be used to join, fuse and/orstabilize a plurality of vertebrae in the thoracic, lumbar, and sacralportions of the spine. For example, to treat spinal disorders such asdegenerative scoliosis, the L5 vertebra to the S1 vertebrae can be fusedusing a system of implants and rods as described herein. As illustratedin FIGS. 8A-18E, the implant structure can include a stem portion and ahead portion. The stem portion can be formed similarly to the SI-Jointimplants described herein and in co-pending U.S. Patent ApplicationPublication 2013/0296953, filed May 6, 2013, titled “FenestratedImplant” and U.S. Pat. No. 8,202,305 titled “Systems and Method for theFixation or Fusion of Bone.” A tulip or saddle structure can be attachedto the head portion, and a rod can be inserted into and fixed to aplurality of tulip structures attached to implanted implant structures,thereby fusing and/or stabilizing the spine and/or other bones. In someembodiments, the stem portion, head portion, and tulip or saddlestructure can all be cannulated and have a lumen that extendslongitudinally through the assembled structure such that the assembledstructure can be disposed over a guidewire or guide pin.

In some embodiments, as illustrated in FIGS. 8A-8C, the head portion 804can be separate from the stem portion 802. For example, FIGS. 8A-8Cillustrate embodiments of the implant structure 800 with a machine tapersuch as a Morse Taper. In some embodiments as illustrated in FIG. 8A,the head portion 804 can have a ball portion 806 and a tapered shank808. The tapered shank 808 can fit into a corresponding tapering cavity810 in the stem portion 802 to form a taper lock that is held togetherby friction. The length of the tapered shank 808 can be varied, makingthe distance between the ball portion 806 and proximal end of the stemportion 802 variable.

In some embodiments as illustrated in FIG. 8B, the head portion 804 canhave a tapering cavity 810 while the stem portion 802 can have a taperedshank 808 extending from the proximal end of the stem portion 802. Thelength of the tapered shank 808 can be varied so that the distancebetween the head portion 804 and stem portion 802 can be adjusted asdesired. In some embodiments, the tapered shank 808 of the stem portion802 can be angled or curved with respect to the longitudinal axis of thestem portion 802. A curved tapered shank 808 can be useful as describedbelow for the embodiment shown in FIG. 8C.

In some embodiments as illustrated in FIG. 8C, the head portion 804 canhave a ball portion 806 and a tapered shank 808 that is curved or angledsuch that the distal portion of the tapered shank 808 is offset orangled with respect to the ball portion 806 and proximal portion of thetapered shank 808. A curved tapered shank 808 can be useful when asuitable implantation location in one or more bones is not aligned withthe other implantation locations. In order for the implant structures800 to line up with the stabilizing rod, a curved tapered shank 808 canbe used so that the head portions 806 all line up with the stabilizingrod even if the implantation locations do not line up.

FIG. 9 illustrates another embodiment of an implant structure 900 with astem portion 902 and a head portion 904. The head portion 904 can have aball portion 906 and a shank 908. The shank 908 can have threads 910,like a screw, that can be screwed into a cavity 912 with complementaryinternal threads. The ball portion 904 can have a screw drive 914 thatfacilitates turning of the head portion 904. The screw drive 914 can bea slot, socket (square, hex, star, etc.), or other typical screw drive914 mechanism.

FIGS. 10A and 10B illustrate embodiments of integrated implantstructures 1000 having a stem portion 1002 and a head portion 1004 thatis integral with the stem portion 1002. As shown in FIGS. 10A and 10B,the head portion 1004 is integral or fixed to the stem portion 1002, andtherefore the head portion 1004 has a fixed length relative to the stemportion 1002. As shown in FIG. 10A, the head portion 1004 can have aball portion 1006 that can be attached to a tulip portion that isdescribed in further detail below in, for example, FIGS. 13A and18A-18C. Alternatively, as shown in FIG. 10B, the head portion 1004 canhave a tulip portion 1007 integrated directly with the stem portion1002. Having an integrated implant structure 1000 can be useful when itis known in advance that an implant structure 1000 will be used in, forexample, a fixation or stabilization procedure that requires the use ofan implant structure with a head portion 1004. The integrated implant1000 can reduce procedure time by not requiring the attachment of thehead portion 1004 onto the stem portion 1002. In addition, because thehead portion 1004 is integral with the stem portion 1002, the integratedimplant 1000 may have a greater structural integrity or strength than animplant assembled from separate pieces.

In some embodiments that may be particularly suited for pedicle screwsalvage as illustrated in FIGS. 11A and 11B, the implant structure 1100can have a stem portion 1102 with ledges or fenestrations 1003 thatpromote bone ingrowth. Examples of fenestrations that can beincorporated into the implant structure 1100 are described in co-pendingU.S. Patent Application Publication 2013/0296953, filed May 6, 2013,titled “Fenestrated Implant.” In some embodiments, the outer surfaceand/or structure of the stem portion 1102 can be twisted. In someembodiments, the stem portion 1102 may have a round cross-section tobetter match the cavity within the bone after the old pedicle screw hasbeen removed. In some embodiments, the stem portion 1102 can be tapered.The diameter, shape and profile of the stem portion 1102 can match thebone cavity. In some embodiments, the stem portion 1102 can be oval,round, square, triangular, or rectilinear. In some embodiments, the headportion 1104 can be attached to the stem portion 1102 as describedabove. For example, the head portion 1104 can be attached to the stemportion 1102 using a Morse taper or screw attachment, or the headportion 1104 can be integral with the stem portion. Pedicle screwsalvage can be performed when an implant, such as a pedicle screw,becomes loose within the bone due to windshield wipering or butterflyingeffects caused by stresses exerted to the bone by the implant. The looseimplant can be removed and then replaced by one of the implantsdescribed herein.

FIG. 12 illustrates an implant structure 1200 with a stem portion 1202,a head portion 1204 attached to the proximal end of the stem portion1202, and an anchor 1210 located distally the distal end of the stemportion 1202. The anchor 1210 can be folded into a collapsedconfiguration during insertion of the implant structure 1200 into bone,and then unfolded and/or expanded into an expanded configuration afterinsertion. In some embodiments, the anchor 1210 can have one or more armportions 1212 that are foldable and/or expandable. In some embodiments,the anchor 1210 can be mechanically actuated from the collapsedconfiguration to the expanded configuration. In some embodiments, thearm portions 1212 can be joined at a hinge or a hub 1214. In someembodiments, the arm portions 12 can be expanded like the frame of anumbrella. In other embodiments, the anchor 1210 can be self-expandingand can be made of a shape memory material such as a nickel titaniumalloy. In some embodiments, the anchor 1210 can be restrained by asheath or other restraining element when in the collapsed configuration.In some embodiments, the anchor 1210 can be attached to and/or extendfrom the distal end of the stem portion 1202. The anchor 1210 can reduceor prevent implant structure 1200 migration after implantation.

FIGS. 13A and 13B illustrate an implant structure 1300 and acorresponding tulip or saddle structure 1350 that can be attached to thehead portion 1304 of the implant structure 1300. The tulip structure1350 can have a slot 1352 for receiving a rod 1380 that can be used tostabilize the spine. In some embodiments, the tulip structure 1350 canhave internal threading 1354 on the two wall portions 1356 that form theslot 1352. In some embodiments, a locking screw 1390 can be used to lockand secure the rod 1380 in place within the tulip structure 1350. Thelocking screw 1390 can have threading 1392 that correspond to theinternal threading 1354 on the two wall portions 1356. To lock andsecure the rod in place, the locking screw can simply be screwed inplace over the rod 1380. The locking screw 1390 can have a screw drivesimilar to screw drive 914 described above with respect to FIG. 9. Inother embodiments, other fastening mechanisms can be used in place ofthe locking screw 1390 to hold the rod in place. In some embodiments,the top portions of the wall portions 1356 can be snapped off along abreak line 1358. In some embodiments, the break line 1358 can be formedby scoring or thinning the wall portions 1356 along the break line 1358.In some embodiments, the tulip structure 1350 does not have any breaklines 1358 or excess wall portions 1356 that can be broken off and caninstead have wall portions 1356 that are sized to receive the rod 1380and locking screw 1390 without having excess material extending past thelocking screw 1390.

FIG. 14 illustrates another embodiment of an implant structure 1400having a stem portion 1402 with a cavity 1412 for receiving anexpandable attachment 1410 on the shank 1408 of the head portion 1404.The expandable attachment 1410 on the shank 1408 can have a collapsedconfiguration and an expanded configuration. The entrance to the cavity1412 can be a narrowed opening 1414 with a diameter less than thediameter of the cavity 1412. The shank 1408 can be inserted through thenarrowed opening 1414 and into the cavity 1412 with the expandableattachment 1410 in the collapsed configuration. Once in the cavity 1412,the expandable attachment 1410 can expand into the expandedconfiguration, thereby securing the head portion 1404 to the stemportion 1402. The head portion 1404 can have a ball portion 1406 forconnected to a tulip structure.

FIG. 15 illustrates another embodiment of a head portion 1504 that canbe secured into a cavity 1412 in a stem portion 1402 similar to thatillustrated in FIG. 14. The head portion 1504 can have a ball portion1506 and a shank 1508 with narrowed or undercut portion 1508 and atapered distal portion 1510. The tapered distal portion 1510 has an endthat is narrow enough to be inserted into the narrowed opening 1414. Asthe tapered distal portion 1510 is further inserted through the narrowedopening 1414, the tapered distal portion 1510 forces the narrowedopening to open wider until the narrowed opening snaps into the undercutportion 1508 of the shank 1508, which in combination with the tapereddistal portion 1510 in the cavity, functions to secure the head portion1504 to the stem portion 1402.

FIG. 16 illustrates another embodiment of a head portion 1604 than canbe screwed into an implant structure 1600 in a similar manner asdescribed in connection with FIG. 9, except that in this embodiment, theshank 1608 can have a length that allows the shank 1608 to extendcompletely through the implant structure 1600. Similarly to theembodiment described in FIG. 9, the shank 1608 can be threaded 1610 anda screw drive on the head portion 1604 can be used to turn the screwlike shank 1608. In some embodiments, the threads 1610 on the proximalportion of the shank 1608 can be machine threads for engaging thecorresponding threads in the implant structure 1600. The threads 1610 onthe distal portion of the shank 1608 can be deeper than the machinethreads, which allow the threads to better engage cancellous bone. Insome embodiments, the pitch of the threads 1610 can be constant alongthe length of the shank 1608. In other embodiments, the pitch of thethreads 1610 can vary between the different thread types.

FIG. 17 illustrates another embodiment of the attachment of the stemportion 1702 of an implant structure 1700 to a head portion 1704. Inthis embodiment, the stem portion 1702 has a socket 1708 for receiving acorresponding ball 1706 on the distal end of the head portion 1704. Theball 1706 can reside in the socket 1708 to form a ball and socket jointthat permits the head portion 1704 to be rotated through a predeterminedangle of rotation. In some embodiments, the angle of rotation can beabout 60 degrees or less. In other embodiments, the angle of rotationcan be between about 30 to 90 degrees or less.

FIGS. 18A-18E illustrate embodiments of a snap-on tulip or saddlestructure 1850. In some embodiments, the tulip structure 1850 can have aslot 1852 for receiving a rod that can be used to stabilize the spine orother bones. In some embodiments, the tulip structure 1850 can haveinternal threading on the two wall portions 1856 that form the slot1852. In some embodiments, the wall portions 1856 can have extended tabsthat can be snapped off and removed. In some embodiments, the tulipstructure 1850 can have a head portion receiving slot 1858 shaped toreceive the head portion 1804 attached to the implant structure 1800.The head portion receiving slot 1858 can be located on the distal end ofthe tulip structure 1850 and provides access to the internal cavity ofthe tulip structure 1850. The distal end of the tulip structure can havean opening 1860 that allows a portion of the implant structure 1800 toextend through. The diameter or size of the opening 1860 is less thanthe diameter or size of the head portion 1804, which allows the tulipstructure 1850 to receive and then retain the head portion within thecavity of the tulip structure 1850. A stabilizing rod can then be fixedin place within the slot 1852 of the tulip structure 1850, therebysecuring the head portion 1804 to the tulip structure 1850.

In some embodiments, the head portion receiving slot 1858 runs up both aportion of one of the side walls and the along the bottom portion to theopening 1860. In some embodiments, the upper portion of the head portionreceiving slot 1858 can be circular in shape to accommodate the ballportion of the head portion 1804. The circular portion of the headportion receiving slot 1858 can be located a sufficient distance fromthe bottom portion of the tulip structure 1850 such that after the ballportion of the head portion 1804 passes into the cavity of the tulipstructure 1850, the ball portion drops down against the bottom portionwhich prevents the ball portion from inadvertently sliding out of thetulip structure 1850. In order for the ball portion of the head portion1804 to be removed from the tulip structure 1850, the ball portion mustbe raised from the bottom of the tulip structure 1850 until the ballportion is aligned with the circular portion of the head portionreceiving slot 1858, and then the head portion 1804 can be removed fromthe tulip structure. In some embodiments, the portion of the headportion receiving slot 1858 on the bottom part of the tulip structurecan be a straight slot. In other embodiments, the portion of the headportion receiving slot 1858 on the bottom part of the tulip structurecan be a curved slot.

The shape and structure of the tulip structure 1850 cavity and opening1860 allows the tulip structure 1850 to have about a 60 degree angle ofmovement and rotation after being attached to the head portion 1804.Such a tulip structure 1850 and head portion 1804 can be referred to aspoly-axial, meaning the tulip structure 1850 can freely move within aconical area. In other embodiments, the angle of movement and rotationcan be between about 30 to 90 degrees or less. Having a substantialangle of movement and rotation allows the implant structure 1800 to beinserted in a wider variety of angles while still allowing the tulipstructure 1850 to be aligned with the rod for fixation.

Any of the implants described herein can be used in a variety ofsurgical procedures, such as stabilization, fixation or fusion of thesacroiliac joint and/or the spine, including vertebra and facet joints.In addition, surgical procedures using a posterior or a posterolateralapproach will be particularly suitable for use with the implantstructures described herein since the tulip structure of the implantwill be aligned with the other implants along the spine afterimplantation. As described herein, these implant structures can beconnected together using a rod that can be secured to each tulipstructure. For simplicity, the following procedures will be illustratedand described using a general implant structure 20, but it is understoodthat any of the implant structures described herein can be used in placeof the general implant structure 20.

For example, FIGS. 19A and 19B illustrate a lateral view and an axialview of an embodiment of the implant structure crossing the SI-Jointusing a posterolateral approach entering from the posterior iliac spineof the ilium, angling through the SI-Joint, and terminating in thesacral alae.

The posterolateral approach involves less soft tissue disruption thatthe lateral approach, because there is less soft tissue overlying theentry point of the posterior iliac spine of the ilium. Introduction ofthe implant structure 20 from this region therefore makes possible asmaller, more mobile incision. Further, the implant structure 20 passesthrough more bone along the posterolateral route than in a strictlylateral route, thereby involving more surface area of the SI-Joint andresulting in more fusion and better fixation of the SI-Joint. Employingthe posterolateral approach also makes it possible to bypass all nerveroots, including the L5 nerve root.

The set-up for a posterolateral approach is generally the same as for alateral approach. It desirably involves the identification of theSI-Joint segments that are to be fixated or fused (arthrodesed) using,e.g., the Faber Test, or CT-guided injection, or X-ray/MRI of SI-Joint.It is desirable performed with the patient lying in a prone position (ontheir stomach) and is aided by lateral and anterior-posterior (A-P)c-arms. The same surgical tools are used to form the pilot bore 42 overa guide pin 38, except the path of the pilot bore 42 now starts from theposterior iliac spine of the ilium, angles through the SI-Joint, andterminates in the sacral alae. The pilot bore 42 is shaped into thedesired profile using a broach, as before described, and the implantstructure 20 is inserted into the broached bore 48. The implantstructure 20 is tapped through the soft tissue protector over the guidepin 38 from the posterior iliac spine of the ilium, angling through theSI-Joint, and terminating in the sacral alae, until the proximal end ofthe implant structure 20 is flush against the posterior iliac spine ofthe ilium. Because of the anatomic morphology of the bone along theposterolateral route, it may be advisable to introduce implantstructures of difference sizes, with the most superior being the longestin length, and the others being smaller in length.

FIG. 20A shows, in an exploded view prior to implantation, arepresentative configuration of an assembly of one or more implantstructures 20 sized and configured to achieve translaminar lumbar fusionin a non-invasive manner and without removal of the intervertebral disc.FIG. 20B shows the assembly after implantation, respectively, in aninferior transverse plane view.

As can be seen in the representative embodiment illustrated in FIGS. 20Aand 20B, the assembly comprises two implant structures 20. The firstimplant structure 20 extends from the left superior articular process ofvertebra L5, through the adjoining facet capsule into the left inferiorarticular process of vertebra L4, and, from there, further through thelamina of vertebra L4 into an interior right posterolateral region ofvertebra L4 adjacent the spinous process. The second implant structure20 extends from the right superior articular process of vertebra L5,through the adjoining facet capsule into the right inferior articularprocess of vertebra L4, and, from there, further through the lamina ofvertebra L4 into an interior left posterolateral region of vertebra L4adjacent the spinous process. The first and second implant structures 20cross each other within the medial lamina of vertebra L4.

The first and second implant structures 20 are sized and configuredaccording to the local anatomy. The selection of a translaminar lumbarfusion (posterior approach) is indicated when the facet joints arealigned with the sagittal plane. Removal of the intervertebral disc isnot required, unless the condition of the disc warrants its removal.

A posterior procedure for implanting the assembly of implant structures20 shown in FIGS. 20A and 20B comprises (i) identifying the vertebrae ofthe lumbar spine region that are to be fused; (ii) opening an incision,which comprises, e.g., with the patient lying in a prone position (ontheir stomach), making a 3 mm posterior incision; and (iii) using aguide pin to establish a desired implantation path through bone for thefirst (e.g., left side) implant structure 20, which, in FIGS. 20A and20B, traverses through the left superior articular process of vertebraL5, through the adjoining facet capsule into the left inferior articularprocess of vertebra L4, and then through the lamina of vertebra L4 intoan interior right posterolateral region of vertebra L4 adjacent thespinous process. The method further includes (iv) guided by the guidepin, increasing the cross section of the path; (v) guided by the guidepin, shaping the cross section of the path to correspond with the crosssection of the implant structure; (vi) inserting the implant structure20 through the path over the guide pin; (vii) withdrawing the guide pin;and (viii) using a guide pin to established a desired implantation paththrough bone for the second (e.g., right side) implant structure 20,which, in FIGS. 20A and 20B, traverses through the right superiorarticular process of vertebra L5, through the adjoining facet capsuleinto the right inferior articular process of vertebra L4, and throughthe lamina of vertebra L4 into an interior left posterolateral region ofvertebra L4 adjacent the spinous process. The physician repeats theremainder of the above-described procedure sequentially for the rightimplant structure 20 as for the left, and, after withdrawing the guidepin, closes the incision.

The intimate contact created between the bony in-growth orthrough-growth region 24 along the surface of the implant structure 20across the facet joint accelerates bony in-growth or through-growthonto, into, or through the implant structure 20, to accelerate fusion ofthe facets joints between L4 and L5. Of course, translaminar lumbarfusion between L5 and S1 can be achieved using first and second implantstructures in the same manner.

FIG. 21A shows, in an exploded view prior to implantation, arepresentative configuration of an assembly of one or more implantstructures 20 sized and configured to lumbar facet fusion, in anon-invasive manner and without removal of the intervertebral disc.FIGS. 21B and 21C show the assembly after implantation, respectively, inan inferior transverse plane view and a lateral view.

As can be seen in the representative embodiment illustrated in FIGS. 21Ato 21C, the assembly comprises two implant structures 20. The firstimplant structure 20 extends from the left inferior articular process ofvertebra L4, through the adjoining facet capsule into the left superiorarticular process of vertebra L5 and into the pedicle of vertebra L5.The second implant structure 20 extends from the right inferiorarticular process of vertebra L5, through the adjoining facet capsuleinto the right superior articular process of vertebra L5 and into thepedicle of vertebra L5. In this arrangement, the first and secondimplant structures 20 extend in parallel directions on the left andright pedicles of vertebra L5. The first and second implant structures20 are sized and configured according to the local anatomy. Theselection of lumbar facet fusion (posterior approach) is indicated whenthe facet joints are coronally angled. Removal of the intervertebraldisc is not necessary, unless the condition of the disc warrants itsremoval.

A posterior procedure for implanting the assembly of implant structures20 shown in FIGS. 21A to 21C comprises (i) identifying the vertebrae ofthe lumbar spine region that are to be fused; (ii) opening an incision,which comprises, e.g., with the patient lying in a prone position (ontheir stomach), making a 3 mm posterior incision; and (iii) using aguide pin to established a desired implantation path through bone forthe first (e.g., left side) implant structure 20, which, in FIGS. 21A to21C, traverses through the left inferior articular process of vertebraL4, through the adjoining facet capsule into the left superior articularprocess of vertebra L5 and into the pedicle of vertebra L5. The methodfurther includes (iv) guided by the guide pin, increasing the crosssection of the path; (v) guided by the guide pin, shaping the crosssection of the path to correspond with the cross section of the implantstructure 20; (vi) inserting the implant structure 20 through the pathover the guide pin; (vii) withdrawing the guide pin; and (viii) using aguide pin to establish a desired implantation path through bone for thesecond (e.g., right side) implant structure 20, which, in FIGS. 21A to21C, traverses through the right inferior articular process of vertebraL4, through the adjoining facet capsule into the right superiorarticular process of vertebra L5 and into the pedicle of vertebra L5.The physician repeats the remainder of the above-described proceduresequentially for the right implant structure 20 as for the left and,withdrawing the guide pin, closes the incision.

The intimate contact created between the bony in-growth orthrough-growth region 24 along the surface of the implant structure 20across the facet joint accelerates bony in-growth or through-growthonto, into, or through the implant structure 20, to accelerate fusion ofthe facets joints between L4 and L5.

Of course, transfacet lumbar fusion between L5 and 51 can be achievedusing first and second implant structures in the same manner.

FIG. 22A shows, in an exploded view prior to implantation, anotherrepresentative configuration of an assembly of one or more implantstructures 20 sized and configured to achieve fusion between lumbarvertebra L5 and sacral vertebra 51, in a non-invasive manner and withoutremoval of the intervertebral disc. FIGS. 22B and 22C show the assemblyafter implantation.

As FIGS. 22A and 22B show, the one or more implant structures areintroduced in a posterolateral approach entering from the posterioriliac spine of the ilium, angling through the SI-Joint into and throughthe sacral vertebra 51, and terminating in the lumbar vertebra L5. Thispath and resulting placement of the implant structures 20 are also shownin FIG. 22C. In the illustrated embodiment, two implant structures 20are placed in this manner, but there can be more or fewer implantstructures 20. Also in the illustrated embodiment, the implantstructures 20 are triangular in cross section, but it should beappreciated that implant structures 20 of other cross sections aspreviously described can be used.

The posterolateral approach involves less soft tissue disruption thanthe lateral approach, because there is less soft tissue overlying theentry point of the posterior iliac spine of the ilium. Introduction ofthe implant structure 20 from this region therefore makes possible asmaller, more mobile incision.

The set-up for a posterolateral approach is generally the same as for alateral approach. It desirably involves the identification of the lumbarregion that is to be fixated or fused (arthrodesed) using, e.g., theFaber Test, or CT-guided injection, or X-ray/MRI of the L5-S1 level. Itis desirable performed with the patient lying in a prone position (ontheir stomach) and is aided by lateral and anterior-posterior (A-P)c-arms. The same surgical tools are used to form the pilot bore over aguide pin (e.g., on the right side), except the path of the pilot borenow starts from the posterior iliac spine of the ilium, angles throughthe SI-Joint, and terminates in the lumbar vertebra L5. The broachedbore is formed, and the right implant 20 structure is inserted. Theguide pin is withdrawn, and the procedure is repeated for the leftimplant structure 20, or vice versa. The incision site(s) are closed.

The assembly as described makes possible the achievement of trans-iliaclumbar fusion using a posterolateral approach in a non-invasive manner,with minimal incision, and without necessarily removing theintervertebral disc between L5 and 51.

FIG. 23A shows, in an exploded view prior to implantation, arepresentative configuration of an assembly of one or more implantstructures 20 sized and configured to stabilize the spondylolisthesis atthe L5/S1 articulation. FIGS. 23B and 23C show the assembly afterimplantation.

As shown, the implant structure 20 extends from a posterolateral regionof the sacral vertebra 51, across the intervertebral disc into anopposite anterolateral region of the lumbar vertebra L5. The implantstructure 20 extends in an angled path (e.g., about 20 degrees to about40 degrees off horizontal) through the sacral vertebra 51 in a superiordirection, through the adjoining intervertebral disc, and terminates inthe lumbar vertebra L5.

A physician can employ a posterior approach for implanting the implantstructure 20 shown in FIGS. 23A, 23B, and 23C, which includes forming apilot bore over a guide pin inserted in the angled path from theposterior of the sacral vertebra 51 through the intervertebral disc andinto an opposite anterolateral region of the lumbar vertebra L5, forminga broached bore, inserting the implant structure 20, and withdrawing theguide pin. The incision site is then closed. As previously described,more than one implant structure 20 can be placed in the same manner tostabilize a spondylolisthesis.

The physician can, if desired, combine stabilization of thespondylolisthesis, as shown in FIG. 23A/B/C, with a reduction,realigning L5 and S-1. The physician can also, if desired, combinestabilization of the spondylolisthesis, as shown in FIG. 23A/B/C (withor without reduction of the spondylolisthesis), with a lumbar facetfusion, as shown in FIGS. 21A to 21C. The physician can also, ifdesired, combine stabilization of the spondylolisthesis, as shown inFIG. 23A/B/C, with a decompression, e.g., by the posterior removal ofthe spinous process and laminae bilaterally.

In addition, in some embodiments as shown in FIG. 24, a posteromedialapproach can be used to insert the implant 2400. For example, theimplant 2400 can be inserted through the posterolateral sacrum, acrossthe alae, through the SI-joint, and into the ilium where the implant mayterminate. As illustrated, the implant 2400 can have a stem portion 2402that is inserted into the bone and a tulip portion 2404 (which may be aseparate component coupled to the implant in any of the examples herein)that remains outside the bone. In some particular implementations, aparticular posteromedial approach may be used which is known as an S2alar-iliac (S2AI) approach. The entry point for the S2AI approach islocated at the midpoint between the S1 and S2 foramen and 2 mm medial tothe lateral sacral crest. The guidewire and or implant should be placedacross the sacro-iliac joint above the superior rim of the sciaticnotch.

Any of the implants herein, including any of the composite implantsherein, may be implanted based on the general illustration in FIG. 24.

In some implementations, just one implant is placed across each SI-jointusing an S2AI trajectory, as depicted in FIG. 24. In otherimplementations, an implant can be added above and or below each S2AIimplant using a lateral approach through the ilium, the SI-Joint, andinto the sacrum, such as depicted in FIGS. 6A-7B.

It should be noted that, according to aspects of the present disclosure,a tulip, saddle structure, poly-axial joint, fastening mechanism orother coupling device (such as shown in FIGS. 13A and 13B) can becoupled to the proximal end of any number of bone anchors. For example,a coupling device may be attached to the proximal end of any of theimplants previously shown in this disclosure, such as those shown inFIGS. 1 and 8A-18E, to allow the implant to couple with a spinal rod orconstruct, such as rod 1380 shown in FIG. 13B. In a similar manner, acoupling device may be located on the proximal end of the implant shownin FIGS. 1-2 or the implant shown in FIGS. 31-34 of U.S. Pat. No.8,734,462. In some embodiments, a coupling device may be attached to theproximal end of any of the implants shown in FIGS. 1B-2B, 9A-9B and10A-10B of U.S. Patent Application Publication 2013/0245763. In someembodiments, a coupling device may be attached to the proximal end ofany of the implants shown in FIGS. 47-49 of U.S. Patent ApplicationPublication 2017/0007409. In some embodiments, a coupling device may beattached to the proximal end of the implant shown in FIG. 12 of U.S.Pat. No. 9,662,157. In some embodiments, a coupling device may beattached to the proximal end of any of the implants shown in FIGS. 7A-9Bof U.S. Patent Application Publication 2016/0081810. In someembodiments, a coupling device may be attached to the proximal end ofany of the implants shown in FIGS. 11-27 of U.S. Patent Application62/649,466. In some embodiments, the proximal ends of two or moreimplants may be joined together with a bridging structure that includesa coupling device for attaching to a spinal rod. In some embodiments, animplant can resemble a staple with two or more prongs for inserting intobone, the implant having a coupling device located on its proximal end.

FIGS. 25A-25G show another exemplary embodiment of a bone implant havinga tulip or coupling device provided at its proximal end (which can be aseparate component secured to the implant in a separate tulip couplingstep). As best seen in FIG. 25B, implant 2500 includes a shank portion2502, a body portion 2504 (which may be referred to herein as a sleeve)and a head portion 2506. Any of the head portions herein may be referredto generally as a tulip, may be a separate component than the implant,and can be secured to the implant after the implant has been implantedin place. In this embodiment, the distal end of shank portion 2502includes threads 2508 for threading the shank portion 2502 into a bonesegment. Threads 2508 may include one or more self-tapping cutouts 2510,as best seen in FIG. 25E. The proximal end of shank portion 2502 may beprovided with a hexagonal recess (not shown) or other suitable featureto mate with a driver to screw the shank portion 2502 into the bonesegment. A central lumen 2512 may be provided along the longitudinalaxis of shank portion 2502 to allow it to be placed over a guidewire orguide pin when being implanted.

In this embodiment, body portion 2504 is provided with a central lumen2514 configured to slide over the proximal end of shank portion 2502.Radially outward extending splines 2516 may be provided at one or morelocations on shank portion 2502, as best seen in FIG. 25B, to mate withcorresponding grooves along the inner surface of central lumen 2514.Splines 2516 and/or other non-rotating features may be provided on shankportion 2502 and body portion 2504 to prevent the two parts fromrotating relative to one another. Splines 2516 and or theircorresponding grooves may be tapered to create a tight fit when bodyportion 2504 is tapped into place over shank portion 2502. Splines maybe omitted in the middle of shank portion 2502 as shown to reduce stressconcentrations and thereby increase fatigue properties of the implant.In other embodiments (not shown), these non-rotation features may beomitted to permit body portion 2504 to rotate relative to shank portion2502.

In this embodiment, body portion 2504 has a triangular cross-section toprevent it from rotating relative to surrounding bone. When body portion2504 is placed across a joint or fracture between two bone segments aspreviously described, body portion 2504 inhibits the two bone segmentsfrom rotating or translating relative to one another. In otherembodiments (not shown), the body portion may have a square,rectangular, oval or other cross-sectional shape with at least onerectilinear face and/or at least one apex to similarly prevent rotation.When body portion 2504 is prevented from rotating relative to thesurrounding bone by virtue of its non-rotationally shaped cross-section,and when splines 2516 prevent shank portion 2502 from rotating relativeto body portion 2504, shank portion 2502 is prevented from rotatingrelative to the surrounding bone. This arrangement prevents shankportion 2502 from undesirably backing out or migrating further into thebone.

Body portion 2504 may be provided with fenestrations 2518 to allow forbony on-growth, in-growth and through-growth. In this exemplaryembodiment, a repeating pattern of spars and cross-struts creates aplurality of triangularly shaped fenestrations on each face of bodyportion 2504. Each of the fenestrations 2518 opens into the centrallumen 2514 of body portion 2504. In some embodiments, body portion 2504is fabricated using an additive manufacturing process such as 3Dprinting. Further information on designing and manufacturing fenestratedimplants is provided in the applicant's U.S. Pat. No. 9,662,157, filedSep. 18, 2015, and titled “Matrix Implant.” The distal end of bodyportion 2504 may also be provided with tapered and rounded leading edges2520 as shown to facilitate inserting body portion 2504 into one or morebone segments. Trailing edges 2522 having a lesser degree of taper maybe provided on the proximal end of body portion 2504 as shown tofacilitate removal of body portion 2504 from the bone, if desired.Having less taper on trailing edges 2522 permits better engagementbetween the proximal end and surrounding cortical bone surfaces.

Head portion 2506 may be provided with a coupler 2524 and a main body2526 as shown in FIGS. 25A-25E, and a nut (not shown). The nut hasexternal threads that mate with internal threads located in the proximalrecess of main body 2526 to tighten a spinal rod (not shown) against thebottom of channels 2528 in main body 2526. As shown in FIG. 25B, theproximal end of shank portion 2502 may be provided with acircumferential rib or barb 2530 for securing head portion 2506 to shankportion 2502 in a snap-fit manner. In some embodiments, main body 2526is configured to pivot in a poly-axial or spherical manner relative tocoupler 2524 and shank portion 2502. In some embodiments, main body 2526is configured to spin about its main axis relative to coupler 2524 andshank portion 2502. In some embodiments, main body 2526 is configured toimmovable relative to coupler 2524 and/or shank portion 2502.

Referring to FIGS. 25F and 25G, central lumen 2514 of body portion 2504and/or shank portion 2502 may be configured to reduce stressconcentrations on shank portion 2502 to help ensure it does not fail inuse after it has been implanted. In some prior art implants, repetitiveheavy load cycles on the proximal end of shank portion 2502 from aspinal rod connected to the head portion can cause the shank portion tobreak apart. A typical point of failure is where the shank portion 2502exits the proximal end of the body portion 2504. According to aspects ofthe present disclosure, stress concentrations may be reduced in thisarea to permit greater load cycling without implant failure.

In some embodiments, as shown in FIG. 25F, the proximal end of centrallumen 2514 of body portion 2504 may be provided with a curved contour2532 as shown to more evenly distribute forces between shank portion2502 and body portion 2504, thereby reducing stress concentrations. InFIG. 25F, the proximal end of shank portion 2502 is depicted in anunloaded state with solid lines and in a deflected state with dashedlines. The degree of deflection is exaggerated in FIG. 25F for ease ofunderstanding. Curved contour 2532 may be provided on just one side ofcentral lumen 2514 in the direction of maximum force, on opposite sidesof central lumen 2514, or around the entire circumference of centrallumen 2514. In some embodiments, curved contour 2532 may mirror thenatural bending profile of shank portion 2502. In particular, thecontour may be defined by the following beam deflection formulas:

y=(F·x ²)/(6·E·I)(x−3·1)

I=(D ⁴ −d ⁴)π/64

-   -   where    -   x=distance in horizontal direction in FIG. 25F    -   y=distance in vertical direction in FIG. 25F    -   F=force applied to proximal end of shank portion 2502    -   E=modulus of elasticity of shank portion 2502    -   I=moment of inertia of shank portion 2502    -   l=length between where shank portion 2502 is fully supported and        the point of force application    -   D=outside diameter of shank portion 2502    -   d=inside diameter of shank portion 2502

In some embodiments, as shown in FIG. 25G, shank portion 2502′ may beprovided with a spherical portion 2534 and body portion 2504′ may beprovided with a mating spherical socket. Body portion 2504′ may also beprovided with a central lumen 2514′ that tapers outwardly towards bothits proximal and distal ends, as shown. With this arrangement, shankportion 2502′ may pivot within body portion 2504′ when a force isapplied to its proximal end. The tapered portions may be provided onjust one side of central lumen 2514′ in the direction of maximum force,on opposite sides of central lumen 2514′, or around the entirecircumference of central lumen 2514′. When shank portion 2502′ reachesthe end of its pivoting travel, it is supported by a large surface areaof body portion 2504′ at both the proximal and distal ends, and may alsobe supported at spherical portion 2534. These large areas of supportgreatly reduce the stress concentrations found in prior art implants,and allow the implant to withstand greater forces and/or a larger numberof loading cycles without failure. In the embodiments of FIGS. 25F and25G, the outer surface of shank portion 2502/2502′ and/or the innersurface of body portion 2504/2504′ may be highly polished to furtherreduce stress concentrations. In some embodiments the surfaces may havea roughness Ra of between 0.01 and 0.04 microns.

Implant 2500/2500′ may be installed in bone, such as across a bone jointor fracture, in a manner similar to that previously described relativeto FIGS. 2A-2F and FIG. 24 (i.e. in an S2AI trajectory). In particular,the bone may be prepared by inserting a guide pin into bone segments,spinning a cannulated drill over the guide pin to drill a pilot hole inthe bone, and tapping a cannulated broach over the guide pin to create abore shaped to receive body portion 2504. In some embodiments, any orall of these steps may be omitted. Shank portion 2502 may then bethreaded into the pilot hole using a tool attached to the proximal endof shank portion 2502, as previously described. Body portion 2504 maythen be tapped into the bone over the proximal end of shank portion2502. As body portion 2504 engages the splines 2516 located on theproximal end of shank portion 2502, a small rotational adjustment (nomore than 15 degrees, for example), may be needed to rotationally alignbody portion 2504 with the shaped bore. This adjustment may be mademanually, or in some circumstances may occur automatically as thetapered and rounded leading edges 2520 of body portion 2504 engage theshaped bore opening in the bone and automatically rotate the implant asneeded while body portion 2504 is being tapped into place. Once bodyportion 2504 is in place, head portion 2506 may be snapped into place onthe proximal end of shank portion 2502. Head portion 2506 may includeproximally extending tabs as previously described that may be snappedoff at this time. When other portions of a spinal construct (not shown)are also in place, a rod may be placed into channels 2528 and secured inplace with a nut, as previously described.

In embodiments having a separate head portion that is assembled to ashank portion during implantation as described above, a variety ofdifferent head portions can be provided in a kit without having toprovide the entire implant for each head type. For example, headportions can be provided that couple to a 5.0, 5.5, 6.0, or 6.35 mmdiameter rod. Shank portions and body portions may also be provided invarious lengths, widths and or shapes. With this modular approach, aspecific head type may be assembled to a specific shank portion and bodyportion to create a greater number of combinations without having tostock a separate implant for each combination.

In some embodiments, shank portion 2502 can be installed in the bone,and then a broach can be inserted over the proximal end of installedshank portion 2502 to create a shaped bore. After the broach is removed,body portion 2504 may then be installed over shank portion 2502. In someembodiments, the body portion may include an integrated broach such thatthe body portion can be installed without first preparing a shaped borein the bone. In some embodiments, body portion 2504 can be installed inthe bone first, and then shank portion 2502 can be installed into thebone through body portion 2504, with or without head portion 2506attached to shank portion 2502 as it is being installed.

According to aspects of the present disclosure, the arrangement of thecurrent embodiment allows for one portion of an implant to be screwedinto place, another portion to be tapped into place, and the twoportions locked together to take advantage of the anti-rotationalaspects of the tapped in portion. In embodiments without splines orother locking features, the various portions can be implanted separatelyas previously described, or the assembled implant can be installed as asingle unit with the body portion rotating in a shaped bore in the boneas the shank portion is screwed into place. In other embodiments havingreleasable locking features (not shown), the assembled implant can beinstalled as a single unit with the locking feature released, allowingthe shank portion to rotate relative to the body portion. After theimplant is installed, the locking feature can be engaged to preventrotation.

FIGS. 26A-26E show another exemplary embodiment of a bone implant havinga tulip or coupling device provided at its proximal end. Implant 2600includes a shank portion 2602, a body portion 2604 and a head portion2606. Shank portion 2602 and body portion 2604 may be separatecomponents as with previously described implant 2500, or they may beintegrally formed as a single component. In this embodiment, the distalend of shank portion 2602 includes bristles 2608 for securing the shankportion 2602 into a bone segment. Bristles 2608 may be angled proximallyand may be flexible, thereby providing little resistance when beingintroduced distally into a bore within a bone, but locking against thebone and preventing proximal withdrawal from the bone. In someembodiments, bristles 2608 are arranged at a 45 degree angle relative tothe longitudinal axis of the implant 2600. Bristles 2608 may beintegrally formed with shank portion 2602, such as with an additivemanufacturing process. Alternatively, bristles 2608 may be separateelements of the same or different material from shank portion 2602 andinserted into holes formed in shank portion 2602. In some embodiments,head portion 2606 serves to contact the outer surface of the bone toprevent implant 2600 from migrating further into the bone. In otherembodiments (not shown), another element that is larger in size than theimplant bore in the bone may be located on or adjacent to the proximalend of body portion 2604 to prevent implant 2600 from migrating furtherinto the bone while allowing head portion 2606 to maintain a full rangeof motion relative to shank portion 2602. In other embodiments (notshown), bristles 2608 may be replaced with or augmented by rigid barbedelements. Further details relating to the fabrication and use ofbristles and barbs with orthopedic implants may be found in U.S. Pat.No. 5,716,358 to Ochoa et al.

The proximal end of body portion 2604 may be provided with a flatsurface (not shown) to allow shank portion 2602 and body portion 2604 tobe tapped into place together into the bone segment(s). Alternatively,internal threads (not shown) may be provided to allow a slap-hammer orother insertion instrument to be temporarily attached to the proximalend of body portion 2604 to aid in inserting implant 2600. A centrallumen 2612 may be provided along the longitudinal axis of shank portion2602 and body portion 2604 to allow them to be placed over a guidewireor guide pin when being implanted.

In this embodiment, body portion 2604 has a triangular cross-section toprevent it from rotating relative to surrounding bone. When body portion2604 is placed across a joint or fracture between two bone segments aspreviously described, body portion 2604 inhibits the two bone segmentsfrom rotating relative to one another. In other embodiments (not shown),the body portion may have a square, rectangular, oval or othercross-sectional shape with at least one rectilinear face and/or at leastone apex to similarly prevent rotation.

Body portion 2604 may be provided with fenestrations 2618 to allow forbony on-growth, in-growth and through-growth. In this exemplaryembodiment, a repeating pattern of alternating triangularly shapedfenestrations may be provided on each face of body portion 2604. Each ofthe fenestrations 2618 opens into a central lumen of body portion 2604.In some embodiments, body portion 2604 is fabricated using an additivemanufacturing process such as 3D printing. Further information ondesigning and manufacturing fenestrated implants is provided in theapplicant's U.S. Pat. No. 9,662,157, filed Sep. 18, 2015, and titled“Matrix Implant.” The distal end of body portion 2604 may also beprovided with tapered leading edges 2620 as shown to facilitateinserting body portion 2604 into one or more bone segments. Trailingedges 2622 having a lesser degree of taper may be provided on theproximal end of body portion 2604 as shown to facilitate removal of bodyportion 2604 from the bone, if desired. Having less taper on trailingedges 2622 permits better engagement between the proximal end andsurrounding cortical bone surfaces.

Head portion 2606 may be provided with a coupler 2624 and a main body2626 as shown in FIGS. 26A-26E, and a nut (not shown). The nut hasexternal threads that mate with internal threads located in the proximalrecess of main body 2626 to tighten a spinal rod (not shown) against thebottom of channels 2628 in main body 2626. As shown in FIG. 26B, theproximal end of body portion 2604 may be provided with a circumferentialrib or barb 2630 for securing head portion 2606 to body portion 2604 ina snap-fit manner. In some embodiments, main body 2626 is configured topivot in a poly-axial or spherical manner relative to coupler 2624 andshank portion 2602. In some embodiments, main body 2626 is configured tospin about its main axis relative to coupler 2624 and shank portion2602. In some embodiments, main body 2626 is configured to immovablerelative to coupler 2624 and/or body portion 2604.

Implant 2600 may be installed in bone, such as across a bone joint orfracture, in a manner similar to that previously described relative toFIGS. 2A-2F. In particular, the bone may be prepared by inserting aguide pin into bone segments, spinning a cannulated drill bit over theguide pin to drill a pilot hole in the bone, and tapping a cannulatedbroach over the guide pin to create a bore shaped to receive bodyportion 2604. In some embodiments, any or all of these steps may beomitted. Shank portion 2602 and body portion 2604 may then be tappedinto the pilot hole and shaped bore, with or without a tool attached tothe proximal end of body portion 2604, as previously described. Onceshank portion 2602 and body portion 2604 are in place, head portion 2606may be snapped into place on the proximal end of body portion 2604. Insome implementations, shank portion 2602 and body portion 2604 may betapped into place with head portion 2606 already installed on theproximal end of body portion 2604. Head portion 2606 may includeproximally extending tabs as previously described that may be snappedoff at this time. When other portions of a spinal construct (not shown)are also in place, a rod may be placed into channels 2628 and secured inplace with a nut, as previously described.

FIGS. 27A and 27B show another exemplary embodiment of a bone implanthaving a tulip or coupling device provided at its proximal end. Implant2700 is a form of sacral alar iliac (SAI) screw and includes a threadedshank portion 2702, a body portion 2704 and a head portion 2706.Threaded shank portion 2702 and head portion 2706 of implant 2700 aresimilar to those of implant 2500 previously described in reference toFIGS. 25A-25G.

Body portion 2704 includes a porous exterior surface that is configuredto reside across a bone joint and/or a proximal bone segment whenimplanted. In this embodiment, body portion 2704 includes a radiallyinward portion 2708 that is solid and a radially outward portion 2710that is a porous bony in-growth region, as shown in FIG. 27B. Radiallyoutward portion 2710 may be formed from a porous plasma spray coatingwith an irregular surface, which supports stable bone fixation/fusion.This implant structure and the surgical approaches disclosed herein makepossible the placement of larger fusion surface areas designed tomaximize post-surgical weight bearing capacity and provide abiomechanically rigorous implant designed specifically to stabilize theheavily loaded SI-Joint. In other embodiments, the entire shank portionand body portions can be porous.

Implant 2700 can be made of a variety of materials. For example, theimplant can be made of a metal or metal alloy, such as titanium orsteel, or a nonmetallic material such as ceramic or polymer. In someembodiments, the implant material can have a certain latticemicrostructure formed from microparticles. For example, the latticemicrostructure can result in a rough or smooth surface texture,depending on the surface finishing techniques used, such as polishing orapplication of a metal plasma spray. A 3-D printing process may be usedto fabricate some or all of implant 2700, which allows the porosity ofthe implant or printed portions to be controlled. For example, theimplant can have a volume porosity between about 30 and 70 percent, withan average pore size between 100 and 1000 microns. The pores can belargely interconnected, largely unconnected, or a mix of interconnectedand unconnected pores. In some embodiments, the pores can be locatedthroughout the material of the implant, including the inner and outerimplant surfaces. For example, the fusion of the microparticles thatform the implant can result in a porous, semi-porous, or nonporousstructure, depending on the degree of fusion between the microparticles.In other embodiments, the pores can be located in a porous coating thatcan be applied onto the implant. For example, a porous coating can beapplied using a titanium plasma spray process, or another metal plasmaspray process. The coating can be applied to the outer surfaces of theimplant, the interior surfaces of the implant, or both the outer andinterior surfaces of the implant. For example, the coating could bepreferentially applied to the outer surface of a matrixed implant toprovide bony ingrowth and on-growth, and not applied to the innerportion of the implant to maximize bony through-growth within theimplant. Also, the coating can be applied preferentially from proximalto distal, or vice versa. The thickness of a porous coating can bebetween about 500 and 1,500 microns. In addition or alternatively to theporous metal coating, a hydroxyapatite coating can also be applied tothe implant. In some embodiments, the porosity can be varied along thelength of the implant. In some embodiments, the thickness of the coatingcan be varied along the length of the implant. In some embodiments, thethickness of the coating applied to the outer surface can be differentthan the thickness of the inner coating. For example, the outer coatingmay be greater than the inner coating in some embodiments. In otherembodiments, the thickness of the inner and outer coatings can be thesame.

FIGS. 28A and 28B show another exemplary embodiment of a bone implanthaving a tulip or coupling device provided at its proximal end. Implant2800 is a form of sacral alar iliac (SAI) screw and includes a threadedshank portion 2802, a body portion 2804 and a head portion 2806.Threaded shank portion 2802 and head portion 2806 of implant 2800 aresimilar to those of implant 2500 previously described in reference toFIGS. 25A-25G.

Body portion 2804 includes a porous exterior surface that is configuredto reside across a bone joint and/or a proximal bone segment whenimplanted, and may be similar to body portion 2704 previously describedin reference to FIGS. 27A and 27B. In this embodiment, body portion 2804includes fenestrations 2808 that communicate between the exteriorsurface and a central lumen 2810. Fenestrations 2808 may be circular inshape as shown, or may be formed in other shapes. Fenestrations 2808 maybe configured to promote bony on-growth, ingrowth and/or through-growthfor faster implant and/or bone joint fusion.

FIGS. 29A and 29B show another exemplary embodiment of a bone implanthaving a tulip or coupling device provided at its proximal end. Implant2900 is a form of sacral alar iliac (SAI) screw and includes a threadedshank portion 2902, a body portion 2904 and a head portion 2906.Threaded shank portion 2902 and head portion 2906 of implant 2900 aresimilar to those of implant 2500 previously described in reference toFIGS. 25A-25G.

Body portion 2904 includes a porous exterior surface that is configuredto reside across a bone joint and/or a proximal bone segment whenimplanted, and may be similar to body portion 2704 previously describedin reference to FIGS. 27A and 27B. In this embodiment, body portion 2904includes fenestrations 2908 that communicate between the exteriorsurface and a central lumen 2910. Fenestrations 2908 may be oblong andset at an angle, as shown. In this exemplary embodiment, fenestrations2908 are all aligned in the same direction as the threads located on theshank portion 2902, but form a more acute angle with the longitudinalaxis of implant 2900. Additionally, fenestrations 2908 may be providedwith sharp cutting edges, such as along their proximal and/or trailingedges. These cutting edges can scrape bone material from the surroundingbone as implant 2900 is being screwed into place and channel the bonematerial towards central lumen 2910 to create a self-grafting SAI screw.This bone material may then promote faster bone growth in and/or aroundimplant 2900. Fenestrations 2908 themselves may also promote bonyon-growth, ingrowth and/or through-growth for faster implant and/or bonejoint fusion.

FIGS. 30A and 30B show another exemplary embodiment of a bone implanthaving a tulip or coupling device provided at its proximal end. Implant3000 is a form of sacral alar iliac (SAI) screw and includes a threadedshank portion 3002, a body portion 3004 and a head portion 3006.Threaded shank portion 3002 and head portion 3006 of implant 3000 aresimilar to those of implant 2500 previously described in reference toFIGS. 25A-25G.

Body portion 3004 includes a porous exterior surface that is configuredto reside across a bone joint and/or a proximal bone segment whenimplanted, and may be similar to body portion 2704 previously describedin reference to FIGS. 27A and 27B. In this embodiment, a single set ofthreads 3008 extends continuously across shank portion 3002 and bodyportion 3004. On the body portion 3004, the minor diameter or roots ofthreads 3008 may be filled with or formed by a porous material 3010. Themajor diameter or crests of threads 3008 may be formed on top of asleeve of porous material 3010, as shown in FIG. 30B. Alternatively, themajor diameter or crests of threads 3008 may be formed integrally withthe minor diameter or roots, and the porous material 3010 can simplyreside within the roots (not shown.) Porous material 3010 may thenpromote on-growth to body portion 3004 and in-growth to threads 3008.

FIG. 31 illustrates another exemplary implant for use in at least one offusing or stabilizing bony tissue, sized and configured such that whenthe elongate body is implanted via a posterior sacral alar-iliac (“SAI”)trajectory (e.g. S2AI) with a bony entry point between a S1 and a S2foramen, a distal region of the elongate body extends distal to asacro-iliac (“SI”) joint and within the outer surfaces of an ilium, anda proximal region of the elongate body is disposed across the SI joint.The implant includes a distal anchoring region having one or more distalsurface features adapted to anchor the distal anchoring region relativeto iliac bone. The implant also includes a proximal region disposedproximal to the distal region, the proximal region having one or moreproximal surface features adapted that facilitate at least one of bonyon-growth, in-growth, or through-growth. The implant in FIG. 31 is anexample of a composite implant, or an implant that is comprised of twoor more components.

The embodiment in FIG. 31 is similar to some regards to the embodimentsin FIGS. 25A-30B herein. Any suitable feature described with respect tothe embodiments in FIGS. 25A-30B can be included in the embodiments thatfollow, and visa-versa, unless indicated to the contrary. Implant 3100includes distal region 3102 configured for anchoring into bone, such asrelatively denser cortical bone, and proximal region 3104, which isadapted to facilitate at least one of bony on-growth, in-growth, orthrough-growth. Distal region 3102 includes at least one thread 3110,and proximal region 3104 includes at least one thread 3112.

As in the embodiments above, proximal region 3104 is adapted tofacilitate at least one of bony on-growth, in-growth, or through-growth.In this example, the adaption includes a porous surface 3114, which isformed in between one or more threads. The thread 3112 in the centralregion of the proximal region is discontinuous, but has an overallhelical configuration. The proximal region 3104 includes a plurality offenestrations 3113 (which are larger than the pores 3114), a subset ofwhich together are disposed in at least a partial helical configuration,as shown in the figure. In this embodiment multiple subsets of theplurality of fenestrations 3113 are each disposed in a partial helicalconfiguration. At least some of the fenestrations are disposed at thelocation of the thread discontinuities, as shown in the figure.

Implant 3100 includes inner elongate body 3108 and outer elongate body3106. Inner and outer elongate bodies are adapted to stably interfacewith one another to resist relative motion in at least one direction.Inner elongate body 3108 includes the thread 3110 on the distal region3102 of the implant. Outer elongate body 3106 includes the thread 3112on the proximal region 3104 of the implant. Inner elongate body 3108 hasa proximal region 3111 that is non-threaded, which optionally mayinclude a thread that interfaces with an optional internal thread onouter body 3106. Outer body includes a distal region 3107 that includesa dual-lead thread, a central region with a single lead thread, and aproximal dual-thread region 3109. One of the threads from distal region3107 does not continue into the central region with the single thread.Outer body 3106 also includes relatively large fenestrations 3113, aswell as relatively smaller pores 3114 that are in between the threads.Outer elongate body 3106 has a larger outer diameter than inner elongatemember 3108. Outer elongate body 3106 can have an inner diameterradially spaced from the outer diameter of the inner elongate body 3108,thereby creating a volume of space radially between the inner and outerelongate bodies 3106 and 3108.

In this exemplary embodiment the inner and outer bodies each have one ormore features that allow them to be engaged such that relative movementbetween the two is resisted in at least one direction, optionallyresisting rotation. Outer body 3106 includes one or more surface feature3121 disposed at a distal end region of the outer body 3106 sized andconfigured to interface with a protruding feature (optionally linear) oninner elongate body 3108, the interface of which prevents rotationbetween the outer and inner elongate bodies. In this embodiment rotationis prevented at the distal end of the outer elongate body due to theinterfacing features. A wide variety of features can be incorporatedonto the inner and outer elongate bodies to provide this functionality,such as that shown and described with reference to FIG. 25B herein.

When implants herein are implanted in a SAI trajectory (e.g. S2AI) forpositioning across an SI joint (details of which are described elsewhereherein), a portion of the implant that has one or more surface featuresspecifically adapted to facilitate at least one of bony on-growth,in-growth, or through-growth should be positioned at the location of theSI joint. FIGS. 32A and 32B illustrate imaging showing an SAI trajectoryfor implanting an SI joint stabilization implant across a SI joint, withthe arrow indicating the trajectory. “Joint length” is a distance fromthe entry point in the sacrum to the subject's SI joint. “Overalllength” is a distance from the entry point in the sacrum to the outerboundary of the subject's iliac cortex. Additionally, a distal portionof the implant that will be positioned distal to the SI joint preferablyhas one or more surface features (e.g., threaded region(s)) that adaptthe distal region to effectively anchor in the relatively more denseiliac cortical bone. An important consideration for implantable devicesthat are implanted across an SI in an SAI trajectory is designing andconfiguring different regions of the implant based on the tissue thatwill be adjacent to the region(s) when implanted.

With respect to FIG. 31, for example, implant 3100 includes pores 3114that span a length so that when implanted in an S2AI trajectory acrossan SI joint, the pores 3114 will be disposed at the location of the SIjoint and will facilitate at least one of bony on-growth, in-growth, orthrough-growth. It is noted that the pores may also extend into distalregion 3102. In this embodiment the single lead thread in the proximalregion 3104 allows more space for the pores to be created in theproximal region 3104 of the implant, in this instance in at least someof the regions between the thread(s). Additionally, distal region 3102,which will be implanted distal to the SI joint in the relatively moredense iliac cortical bone, has one or more surfaces features (e.g.thread(s)) that adapt the distal region 3102 to effectively and betteranchor into the denser bone. In this example, distal region 3102includes a dual lead thread (which may be more than dual), causing it toprovide better anchoring that the single lead thread in the centralregion of proximal region 3104. It is noted that the thread in thecentral region of proximal region 3104 could have a smaller pitch, andstill be adapted to facilitate in growth (e.g. with pores). It is thusunderstood that one or more characteristics (e.g. pitch) of surfacefeatures may be the same in both the proximal and distal regions. Inthis embodiment the pitch is the same, but the distal region has amultiple (dual in this case) lead thread. In the embodiment in FIG. 31,one or more surface features in the proximal and distal regions havedifferent characteristics.

FIGS. 33A-33C illustrate an exemplary embodiment of a composite implantthat can be sized and configured for implantation across an SI joint viaa SAI trajectory (e.g. S2AI). While implant 3300 is described as being acomposite implant composed of a plurality of pieces that are assembledprior to implantation (in this embodiment, two parts), implant 3300 canbe modified to be a single, integral unit, that is manufactured from asingle component. Implant 3300 includes ingrowth region 3304, which issimilar to other implant “proximal regions” herein. Implant 3300 alsoincludes anchoring region 3302, which is similar to other “distalregions” herein. Implant 3300 is similar to implant 3100 in FIG. 31. Anydescription of implant 3100 may be incorporated into implant 3300, andvisa-versa, unless indicated herein to the contrary. Distal anchoringregion 3302 includes double lead threads 3301 and 3301′, and distalregion 3302 is tapered in the distal direction. Proximal ingrowth region3304 includes a plurality of larger fenestration 3306, subsets of whichhave a partial helical formation, as shown. In this embodiment, thread3303 is continuous (unlike thread 3112) with fenestrations 3306 beingdisposed between the thread. Proximal region 3304 also includes pores3305, also disposed between thread 3303. In variations, thread 3303could have one or more discontinuities (like thread 3112), but couldalso have sections that make complete turns (at least 360 degrees) inbetween discontinuities in the thread.

Implant ingrowth region 3304 includes a plurality of fenestrations 3306and smaller pores 3305, both of which extend through an outer surfaceand an inner surface of the proximal region, creating a passageway froman inner implant volume (but not the “innermost” volume in thisembodiment) to a location outside the implant. Fenestrations 3306 andpores 3305 help adapt the proximal anchoring region to facilitatein-growth.

In this embodiment, implant 3300 includes inner component 3320 (e.g., ascrew or screw-like component) and outer component 3340 (e.g., an outersleeve), which are adapted to be secured relative to one another priorto the implant being fully implanted (e.g. secured prior to any part ofthe implant being implanted, or secured at some point during theprocedure), and which are not integrally formed from the same component.The inner component is an example of an inner shank, and the outercomponent is an example of a sleeve. Inner component 3320 and outercomponent 3340 are shown individually, not secured together, in FIG. 33Band FIG. 33C, respectively. In this embodiment, when the inner and outercomponents are secured together, they interface such that relativemotion between the two is restricted in at least one direction (e.g.rotational and/or axial). Inner component can have outer componentinterface 3321 shown in FIG. 33B, which in this embodiment is a threadedregion that can mate with an inner thread on outer component 3340, andwhen interfaced the distal end of the outer component 3340 is secured tothe inner component 3320. The proximal end of outer component can alsobe secured to the inner component, such as with a threaded connection(e.g. that can include proximal threaded region 3323 on the innercomponent). In this embodiment inner component includes a non-threadedregion 3322, which may be a shaft, such as a smooth shaft. Thenon-threaded region can be the internal surface of an inner volumedisposed between the inner component and the outer component.Non-threaded region 3322 can have any number of surface features meantto facilitate ingrowth, such as a roughened or other similar non-smoothsurface. In this embodiment, it is the inner component 3320 thatincludes the distal anchoring region 3302 of implant 3300, which in thisembodiment includes the threads 3301 and 3301′.

FIG. 33C illustrates outer component 3340, which in this embodiment isan outer sleeve that is sized and configured to be advanced over theinner component 3320, the both of which are adapted to be securedrelative to one another to resist relative motion therebetween in atleast one direction. Outer component 3340 has an internal bore extendingtherethrough, wherein fenestrations 3306 are created through the innercomponent 3340, creating communication between the internal bore and theoutside of the implant. At the proximal end region of the outercomponent 3340, there is a second thread 3308, creating a dual threadregion at the proximal end region. Thread 3303 extends to the end of thethread region, and in this exemplary embodiment has a constant pitchalong its length, but in other embodiment the pitch can vary to someextent. While not shown in FIG. 33C, pores 3305 can be in the outercomponent between the threads, as in the embodiment in FIG. 31. Optionalporous regions 3305 are labeled (only two are labeled) but the pores arenot shown in FIG. 33 for clarity. A plurality of individualfenestrations 3306 together extend in a partial helical configuration,even though the fenestrations are considered individual fenestrations.In this embodiment there are three regions of fenestrations that eachextend in a partial helical configuration, as shown in the figures. Thefenestrations 3306 do not extend into the dual-threaded region at theproximal end of the outer component 3340, nor do they extend all the wayto the distal end of the outer component. Any number of thefenestrations 3306 can be tapered (larger outer dimension), as shown.The optional fenestrations can facilitate at least one of bonyon-growth, in-growth, or through-growth, as can the optionalfenestrations.

The plurality of sets of fenestrations 3306 in this embodiment areconfigured and oriented so that a physician can see passing through theouter component from one side to the other using radiographic imaging tomonitor bony ingrowth and fusion over time.

An exemplary advantage of having a composite implant with two (or more)pieces is that a first (e.g. inner shank) component that is moreresistant to fatigue can be manufactured using some common techniques,which may include some common screw manufacturing techniques. The firstcomponent (e.g. inner component) may be made from a material that isrelatively more resistant to fatigue, such as, for example withoutlimitation, titanium or stainless steel. For example, inner component3320 shown in FIG. 33B may be made from a relatively more fatigueresistant material, such as titanium, which provides strength to theimplant 3300. Additionally, distal anchoring region 3302 can bemanufactured using, for example, common screw manufacturing techniques.By selecting a material for the inner component that is stronger andimparts strength to the implant, the second component, such as outercomponent 3340 (e.g., outer sleeve) shown in FIG. 33C, need not be asfatigue resistant. This provides more options for choosing a designand/or material for the second component, which allows for more designoptions for the second component, and can thus make easier the processof imparting additional functionality to the implant using designfeatures of the second component. For example, outer component 3340(e.g., a sleeve) may be designed with certain functionality (e.g.,porous and/or roughened surfaces) that causes it to be less fatigueresistant, and optionally much less fatigue resistant, than the innercomponent. The outer component (e.g., 3340) may be made from a widevariety of materials, such as titanium alloy, polymers, or ceramics. Inthis embodiment, the outer component, which will be referred to as anouter sleeve, provides several features to the implant. By having anaxially extending central bore with an inner diameter greater than theouter diameter of the inner component, the implant has an empty volumebetween the inner and outer component that helps facilitate the ingrowthof tissue therebetween, which helps stabilize the implant afterimplantation. The volume of space can also be used to deliver one ormore agents into the subject after the implant is positioned in thesubject. Additionally, the outer sleeve includes aperture and/orfenestration that can also facilitate the ingrowth of tissue into thevolume. The outer sleeve also includes one or more threads, which helpanchor the implant at the location of the thread(s), which is thisembodiment includes the location of the SI joint.

Any of the composite implants in this disclosure may thus benefit fromthe exemplary advantages of composite implants set forth herein.

As set forth herein, the implants in FIGS. 25-47 may be implanted acrossan SI joint and can be advanced using a SAI trajectory (e.g. S2AI), suchas is generally shown in FIG. 24 herein. As set forth herein, thedifferent regions of the implant can be configured to provide one ormore functions, which may depend on the type of tissue that will beadjacent to the particular region during or after implantation. Forexample, the SAI implants will preferably have a region, such asproximal region 3304 that when implanted and extends across the SIjoint, facilitates at least one of bony on-growth, in-growth, orthrough-growth. As can be seen from FIGS. 32A and 32B, the proximalregion should have a length such that when implanted, will extend acrossthe SI joint. In some embodiments the proximal ingrowth region (e.g.,region 3304) has a distal end that extends at least as far as 20 mm fromthe proximal end of the implant. In this context, the proximal end doesnot necessarily extend all the way to the proximal end of the implant.The proximal region merely has a distal end that is at least 20 mm awaythe proximal end of the implant. In some embodiments the distal end isfrom 20 mm-100 mm from the proximal end of the implant, optionally from30 mm-75 mm, optionally from 30 mm to 60 mm. In this context, “proximalregion” generally refers to a region of the implant that has at leastone structural difference than a distal anchoring region that is closerto the implant distal end than the proximal growth region. In theexemplary embodiment in FIGS. 33A-33C, one of the structural differencesbetween the proximal region and the distal region is that proximalregion has a threaded region with a lower percentage (of its length) ofdual-lead or multi-lead threads. Additional differences in thisembodiment include fenestrations and pores present in the proximalanchoring region. The exemplary lengths of the proximal growth regionsin this embodiment can be incorporated into other SAI implants herein,such as those in FIGS. 25-30. Any of the lengths of the proximal regions(“proximal region” in these contexts may also refer to “proximal growthregions”) in this context can also be a length of the shank or shaftregion 3322 of the inner component.

Other types of implants that may appear to have similar structure anddimensions many not necessary provide the advantages set forth herein.For example, the relative lengths of different sections of the thoseother implants, in combination with the overall length of thoseimplants, may not necessary be sized to provide the benefits herein whenimplanted according to methods set herein. For example, other types ofimplants may not have a distal anchoring section that is sized(including length) and configured for ilium bone anchoring, and aproximal section that is sized (including length) to be positionedacross a SI joint when the distal anchoring region is disposed in theilium, the proximal region adapted to facilitate tissue growth.

The distal anchoring regions (e.g. region 3302 in FIG. 33A) in thiscontext refers generally to a distal region of the implant that does notextend all the way to the proximal end of the implant, and which has oneor more structural differences than a more-proximally disposed region,wherein the distal region has one or more structural features thatbetter adapt the distal region for anchoring to tissue than the moreproximally disposed region. For example, the distal region 3302 has ahigher percentage of dual-lead or multi-lead threads and can be made ofstronger material or as a stronger structure than proximal region 3304,adapting it for better anchoring than a more proximally disposed region.The distal region may or may not extend all the way to the distal end ofthe implant. In the embodiment in FIGS. 33A-C, for example, the distalregion is considered to extend all the way to the distal end of theimplant. The distal end of the distal anchoring region extends at leastas far distally as 40 mm from the proximal end of the implant. Extendingat least this far distally adapts the distal region of the implant tobetter anchor into more dense cortical iliac bone, which will beadjacent the distal region when the implant is implanted in an SAItrajectory. The distal end of the distal region may be from 40 mm to 120mm away from the proximal end of the implant, optionally from 40 mm to100 mm, optionally from 40 mm to 80 mm. The distal end of the implantshould not breach through the iliac bone and extend out of the iliacbone.

In some embodiments the length of the distal region is from 10 mm to 80mm, such as from 10 mm to 60 mm, such as from 10 mm to 50 mm, such asfrom 10 mm to 40 mm, such as from 10 mm to 40 mm, such as 15 mm to 35mm, such as 20 mm to 30 mm.

The proximal region may be longer than the distal region, such as in theembodiments in FIG. 25-33, but in other embodiments the distal regionmay have the length as the proximal region. And as set forth above, the“proximal growth region” (e.g. 3304 in FIG. 33A) may not extend as farproximally as in the embodiments in FIG. 25-33 (but the implant maystill be adapted to adequately facilitate ingrowth, including at thejoint), so the proximal growth region could in some alternativeembodiments be the same length or even shorter than the distal anchoringregion.

In some embodiments the proximal growth region is longer than the distalanchoring region, and in some embodiments is 1-3 times the length of thedistal anchoring region, such as 1.1 times-2.9 times the length of thedistal anchoring region. For example, in the embodiment in FIGS. 33A-C,the proximal growth region is from 1-3 times the length of the distalanchoring region, and is from 1-2 times the length of the distalanchoring region. The relative lengths and ratio may depend on whereinthe implant regions are disposed after implantation, and the functionthat is needed from the different implant regions based on the adjacenttissue.

The distal anchoring region (e.g. region 3302, 3102) may be a doublelead threaded region, such as the embodiment in FIG. 33A-33C. Forexample without limitation, the thread pitch may be from 4 mm-8 mm, suchas from 5 mm to 7 mm (e.g., 6 mm), with the threaded region having a 3mm lead. The dual lead threaded region helps adapt the distal anchoringregion for enhanced anchoring into the harder cortical bone. The implant3100 shown in FIG. 31 also has a distal anchoring region with a duallead threaded region.

In the embodiment in FIGS. 33A-33C, the inner component 3320 includes ashaft region 3322. The shaft outer diameter (“OD”) is less than theinner diameter (“ID”) of the outer sleeve 3340. In some embodiments thedistance (i.e., the spacing) between the OD and the ID may be between0.1 mm and 5 mm, such as from 0.5 mm to 3 mm. As set forth herein, thisspacing creates the volume that facilitates growth therein.

In some merely exemplary embodiments, outer component 3340 (e.g. outersleeve) can have a thread (e.g. 3103) that has a pitch that may beconstant along most of its length, as is the case in FIGS. 33A-33. Thepitch may be from 3 mm to 9 mm, for example (e.g., from 4 mm-8 mm, suchas from 5 mm-7 mm, such as 6 mm), even if the thread has one or morediscontinuities along its length (e.g. as in the embodiment in FIG. 31).The threaded region may be single lead along at least 50% of its lengthor more, as is the case in FIG. 31 and FIGS. 33A-33C, and in theseembodiments the threaded region is single lead along at least 75% of itslength. The pitch of the threaded region of the outer component can bedesigned to maintain enough surface area in the body of the outercomponent to create enough fenestrations (e.g. fenestrations 3114 or3305), which can facilitate growth.

The outer component in FIG. 31 and in FIGS. 33A-33C includes a proximalregion that is dual lead (e.g., 3303 and 3308 in FIG. 33C). Dual-leadand dual-thread are terms that may be used interchangeably in thisdisclosure. The dual (or double) lead region helps better anchor thisregion of the implant into the more dense cortex of the sacrum, similarto how the dual lead anchoring region of the implant can be dual lead toprovide better anchoring in cortical iliac bone. Any of the implantsherein can have this proximal dual lead region.

As set forth herein, the internal surface of the outer component 3340can have an internal threaded region, which is configured to interfacewith external threaded region 3321 (see FIG. 33B) on the inner component3320. This can help secure the internal and outer components.

In some embodiments the outer and inner components are adapted such thatwhen assembled the outer component is put under compression due to thesecured engagement between the two components. Components in bending mayfail on the surface that is exposed to tension, so pre-stressing one ormore components in compression can provide the benefit a higher workingload range. Pre-stressing the outer component is, however, optional. Anyof the implants herein can be pre-stressed in this manner to provide thebenefit of a higher working load range.

With any of the implants herein, the distal end (or proximal end) of theouter component can be secured to the inner component while the proximalend (or distal end) is not secured to resist relative movement in atleast one direction. By allowing the proximal end (or distal end) to befreely moveable relative to the inner component, the implant maybeneficially be less likely to fatigue, due to fewer forces acting onthe implant.

In alternative embodiments, the shaft region of the inner component(e.g. 3322 in FIG. 33B) may include one or more apertures orfenestrations therein, which may be a wide variety of sizes andconfigurations. Having one or more openings in the inner component couldallow a substance (e.g. a therapeutic) to be delivered into an innerchannel or bore in the inner component and out the openings, which couldalso pass through the opening (e.g., apertures, smaller fenestrations)in the outer component and interact with tissue.

It is understood that any suitable feature described with respect to anyof the implants in FIG. 25-33 can be incorporated into any otherembodiment in FIGS. 25-33, particularly if the feature can be clearlyand easily incorporated therein.

Even if not specifically described, the implants disclosed in FIGS.31-47 include a proximal end region that is configured to be coupled toa tulip, and is similar to the tulip or coupling devices or members atthe proximal ends of the implants in FIG. 25-30. Any of the tulip orcoupling devices described in the context of FIGS. 25-30 herein areexpressly incorporated by reference into the embodiments in FIGS. 31-33.The tulip coupling members are configured to enable the implants to becoupled to other bone stabilization systems, which are describedelsewhere herein.

Any of the exemplary features in any of the composite implants hereinmay be integrated or incorporated into other composite implant examplesherein, unless specifically indicated to the contrary.

FIGS. 34A and 34B illustrate side views of an exemplary compositeimplant (assembled) that can be sized and configured for methods ofimplantation across a sacro-iliac (SI) joint via a posterior sacralalar-iliac (“SAI”) trajectory, for example a posterior second sacralalar-iliac (“S2AI”) trajectory. FIG. 34A is an assembled side view(without a tulip coupled thereto), while FIG. 34B is a sectionalassembled view. Implant 3400 includes a sleeve 3410 and shank 3430,wherein the sleeve is sized and configured to be positioned over atleast a portion of the shank. The sleeves herein have an inner lumensized and configured to receive therethrough an inner member. The hasone or more growth surface features adapted to facilitate at least oneof bony on-growth, in-growth, or through-growth. The sleeve ispositioned relative to the shank to form the composite implant with ashank interface feature and a sleeve interface feature interfacing eachother so as to resist relative motion between the sleeve and shank in atleast one direction. A shank herein may be referred to as an inner shankin cases where a sleeve is disposed around at least a portion of theshank. Inner and outer in this context refers to relative radialpositions, relative to an optional long axis of the implant.

In this embodiment, sleeve 3410 is configured such that it can be frontloaded over the shank 3430. That is, the distal end of the shank can beadvanced into the proximal end of the sleeve (relative motion) toassemble the shank and sleeve into the assembled configuration shown inFIGS. 34A and 34B.

Sleeve 3410 includes a tapered distal threaded region 3411, any portionof which may be textured. In this embodiment tapered distal threadedregion 3411 is a dual lead thread. Sleeve 3410 also includes centralregion 3412, which includes a single lead as shown, a plurality offenestrations 3413, and a plurality of discrete lattice sections 3414(only one labeled). In this example, each of (in other embodiments atleast some of) the plurality of fenestrations 3413 is disposed betweenaxially adjacent thread regions, as shown. In this example each of (inother embodiments at least some of) the plurality of lattice sections3413 is disposed between axially adjacent thread regions, as shown. Inthis example multiple subsets of the plurality of fenestrations are eachdisposed to a partial helical configuration, as shown. In this examplemultiple subsets of the plurality of lattice sections are each disposedto a partial helical configuration, as shown.

Implant 3400 includes a distal anchoring region (“DAR” in FIG. 34B) andgrowth region (“GR” in FIG. 34B). The distal anchoring region includesone or more distal surface features (in this embodiment threads) thatbetter adapt the distal anchoring region for anchoring into iliac bonethan the growth region. The growth region includes one or more growthfeatures that better adapt the growth region to facilitate at least oneof bony on-growth, in-growth, or through-growth than the anchoringregion (such as more fenestrations 3413, more lattice sections 3414 andsingle thread versus dual threads).

FIGS. 36A-36C illustrate an exemplary composite implant 3600 that caninclude any relevant feature of any composite implant (multi-component)herein. Any features not specifically described may be incorporated byreference into this embodiment from other examples herein. Similarfeatures may be similarly labeled in the figures. Implant 3600 includessleeve 3610 and shank 3630. In the embodiment in FIGS. 36A-C, sleeve3610 includes a distal tapered threaded region as shown. The distaltapered threaded region includes optional textured surface 3616 on theminor diameter of the threads. As shown in Section B-B from FIG. 36A, asshown in FIG. 36B, lattice sections 3614 are disposed in the sleeveflutes 3615, and the lattice sections 3614. In Section C-C from FIG.36A, as shown in FIG. 36C, however, the sleeve also includes latticesections 3614′ that fill the cutting fluid void. In this proximal regionof the sleeve, the lattice sections 3614′ essentially fill in, or takethe place of, apertures 3613. These through lattice sections 3614′ canincrease the amount of tissue growth through sections 3614′. Also shownin FIG. 36C is a volume (or void) defined between the shank outerdimension and the sleeve inner diameter, in which tissue ingrowth canoccur.

The sleeve in FIG. 36A-36C is adapted to be front loaded onto the shank.Front loading the sleeve makes it easier to match the locations of thethreads on the sleeve and shank.

In any of the composite implant examples herein, the sleeves may bemanufactured by printing.

FIG. 35 illustrates an exemplary shank 3530. Any of the shanks hereinmay also be referred to as an inner member. Shank 3530 includes a distalregion 3540, which is threaded in this embodiment and has a dual threadin this embodiment. Distal region 3540 is tapered.

The shank includes a section 3551 and a section 3552, with section 3553axially in between. Either or both of sections 3551 and 3552 may betextured, such as with TPS, grit blast, HA, for example withoutlimitation, to facilitate one or more of in growth, on-growth, orthrough growth. Section 3553 can include a central thread as shown. Thethread in central section 3553 may be made with the same thread pass asthe pass creating the threads on the distal shank section. A benefit ofthe thread in central section 3553 can be that it creates volume betweenthe sleeve and shank that can increase graft volume while providingsupport to the sleeve.

Any of the inner members herein, such as any shank herein, can bemanufactured by machining the inner member. In some embodiments theinner member can be machined out of a solid material such as titanium.The central rib in section 3553 is an example of a central rib that canbe configured to reduce the bending moment on the shank. This can behelpful for relatively longer shank lengths, such as 80-120 mm lengthshanks.

FIG. 37 illustrates a shank 3700 that includes a central rib 3731. Thecentral rib 3731 is a region with a larger radial dimension thanadjacent sections of the shank, as shown in FIG. 37. The rib canincrease graft volume, while optionally help stabilize the sleeve.

Any of the shanks herein (one any section thereof) may have one or moreholes therethrough, such as to facilitate post-implant administering oneor more agents (e.g. PMMA into the ilium).

In any of the examples herein, the sleeve apertures herein may have oneangled edge to help cut bone while screwing the implant into position,and the other edge can be straight, as shown in the examples in FIGS.34A-47. This can help self-harvest the bone and help fill thefenestrations with bone.

FIG. 40 illustrates a portion of composite implant 4000 that includessleeve 4010 and shank 4030. Optional apertures 4013 are also shown. Anyother feature from any other embodiment herein can be incorporated intoimplant 4000. Implant 4000 includes a shank 4030 that includes optionalplurality of holes 4023 that are adapted to function as post-fill graftports. The holes 4023 can communicate with an inner shank volume tofacilitate post-implant filling. In this embodiment apertures 4023 areoptionally aligned with holes 4023.

FIGS. 41A and 41B illustrate exemplary composite implant 4100 thatincludes sleeve 4110 and shank 4130. In this embodiment (or any otherembodiment herein), sleeve 4110 includes cutting flutes in the distalregion. In this exemplary embodiment, cutting flutes have a 15 degree to25 degree cutting face 4128, as shown in FIG. 41B. The cutting faces maybe angled at other degrees. Implant 4100 includes any other features ofany other composite implant herein.

The implant may have one or more ways in which the sleeve interacts withthe shank to help stabilize the sleeve relative to the shank whenassembled. For example, the shank can have a shank interface feature andthe sleeve can have a sleeve interface feature that are configured tointerface with each other so as to resist relative motion between thesleeve and the inner shank in at least one direction (e.g. axial,radial, rotational). For example, the sleeve and shank may interface inone or both of a distal anchoring region and a proximal region of theimplant to help stabilize the sleeve relative to the shank. In someexamples the shank and sleeve do not interface in a central region ofthe implant.

For example, the shank 4230 may include, in the distal threaded region,a detent, depression, or barb 4239 in a thread, as shown in FIG. 42. Thebarb 4239 can be configured to interface with the sleeve to preventsleeve 4210 from advancing too far distally relative to the shank. Thismay function as a back-up or secondary stop feature if a primary lockingmechanism fails.

The sleeve and the shank may alternatively or in addition to interfacein a proximal end region of the composite implant to resist relativemovement therebetween in at least one direction. FIG. 43 illustrates anexemplary proximal end region locking mechanism, which may beincorporated into any of the composite implants herein. The sidesectional view of FIG. 34B also includes the same or similar proximalend region locking mechanism as that shown in FIG. 43. Composite implant4300 is shown with the sleeve in a model view with lattice regions 4314and 4314′ illustrated as solid regions. Locking ring 4316 (which can bethe same or similar to locking ring 3416 in FIG. 34B) is a separatecomponent, which is configured to snap into grooves in the shank and thesleeve during assembly of the shank and sleeve. The optional annularlock ring functions to prevent potential migration of a loose sleeve.

FIGS. 44A-C are side views of an exemplary composite implant 4400 (FIG.44C shows shank 4410). FIG. 44B is a side sectional view. FIGS. 44A-44Cillustrate additional or alternative ways in which the sleeve and shankcan interface to resist relative motion therebetween in at least onedirection. The shank and sleeve can have interference-fit threads inthread interface region 4450, as shown in the sectional view of FIG.44B, which can help resist relative motion between the shank and sleeve.Any portion(s) of the threads may have no clearance therebetween. Inthese embodiments the sleeve includes internal threads in the distal endregion that are configured to interface with the outer threads on theshank.

Alternatively or in addition to, the shank/sleeve interface can includea tapered locking connection in tapered locking connection region 4460.At this interface region the shank and sleeve can include distal tapersas shown, which together form a taper lock.

Alternatively or in addition to, the shank/sleeve interface can includea proximal end region interface in region 4470, which in this embodimentincludes a tight sliding fit between optionally smooth surface of thesleeve and shank. The surface 4419 of the shank that sleeve interfaceswith is shown in FIG. 44C. FIGS. 44A-44C is an example of a compositeimplant in which the sleeve and shaft interface in distal end regionsand proximal end regions, but does not interface in a central region inbetween the distal and central regions.

In any of the embodiments herein, the sleeve and shank can interface ina distal region, such as in one or both of regions 4450 and/or 4460 inFIG. 44B, but may not interface in a proximal region (e.g., optionallynot in region 4470 in FIG. 44B).

Additionally, if the sleeve and shank interface in a proximal region,the proximal interface region may provide for some relative movementbetween the sleeve and shank, but can still provide some degree ofoverall resistance to movement therebetween in at least one direction.

FIGS. 45A and 45B illustrate (in side and sectional side views,respectively) an exemplary composite implant 4500, including sleeve 4510and shank 4530. Implant 4500 may alternatively or in addition to includeany of the features herein of any other composite implant. Shank 4530illustrates an example of how distal threaded region 4541 and proximalthreaded region 4542 may be cut from a blank starting material duringthe same step so that the threads share the same start. Proximalthreaded 4542 can be dual-lead thread as shown, similar to otherembodiments shown herein. Region 4519 of outer sleeve is dual-lead, aswith other embodiments herein.

FIG. 45B illustrates an exemplary shank/sleeve distal interface thatincludes a threaded interface between sleeve 4510 and shank 4530. In theinterface region 4538 as shown, the shank thread crest optionallybecomes gradually flatter in the proximal direction, as shown. That is,the crest is less flat further distally in region 4538 and becomesflatter moving proximally, as shown in FIG. 45B.

Implant 4500 is an example of a composite implant in which the sleevecan be placed under compression upon assembly of the shank, forexemplary benefits set forth herein. For example, components in bendingmay fail on the surface that is exposed to tension, so pre-stressing oneor more components in compression can provide the benefit of a higherworking load range. Pre-stressing the outer component is, however,optional. Any of the implants herein can be pre-stressed in this mannerto provide the benefit of a higher working load range. Implant 4500includes shank 4530 that includes stop 4539 in the configuration of ashoulder, as shown. The stop 4339 provides a mechanical stop for sleeve4510 and help compress the sleeve (pre-strain), for reasons set forthherein. One separate aspect of this disclosure is thus a compositeimplant wherein an outer member (e.g. sleeve) is put under compressionwhen interfaced with an inner member (e.g. shank). One of the optionalbenefits of pre-straining/pre-compressing the sleeve would be in caseswhere the sleeve might or would be more likely to break before the shankdue to material properties of the sleeve compared to the shank.

FIG. 46A illustrates an exemplary composite implant 4600, includingsleeve 4610 and shank 4630. Implant 4600 may alternatively or inaddition to include any other features of other composite implantsherein. The other composite implants herein may include any feature ofimplant 4600. FIGS. 46B-46D illustrate exemplary features of exemplarysleeve 4610. Any of the sleeves herein may be 3D printed, for example.In the sleeve distal thread region shown in FIG. 46B, the thread mayhave a 5° to 15° back flank angle, for example. FIG. 46C illustrates acentral region of exemplary sleeve 4610 in the more centrally disposedgrowth region of the implant. In this threaded region the thread mayhave a 0° to 3° back flank angle, for example. FIG. 46D illustrates aproximal region of sleeve 4610, which has a dual lead thread. As shown,the sleeve minor diameter surface 4617 tapers radially outward from thedistal end to the proximal end, as shown in both FIGS. 46A and 46D. Themajor diameter can be maintained constant or substantially constant. Thethread may have a 0° to 3° back flank angle, for example. FIG. 46Eillustrates a distal end region of exemplary shank 4630. Any of theshanks herein may be machined using a variety of known machiningprocesses. Thread 4637 has a small flat at the crest, as shown, whichgradually increases in length in the proximal direction, also as shown.The distal shank thread may optionally include a plurality of cuttingflutes in this region, optionally first and second flutes that are 180degrees from each other. The distal shank thread may optionally have a10° to 15° back flank angle, for example.

FIG. 47 is a side view that illustrates an exemplary composite implant4700 that includes outer member 4710 (e.g. sleeve) and inner member 4730(e.g. shank). The inner member, like any of the inner members herein,can include a proximal end 4760 that is configured to be coupled to atulip, to which a reinforcing rod may be secured (details of which aredescribed herein). As set forth herein, different regions of the implantcan be configured to facilitate one or more functions once implanted(e.g. distal anchoring region, growth region, proximal anchoring region,etc.). Those regions can have lengths such that when implanted based ona trajectory (or range of general trajectories, such as posterior sacralalar-iliac (“SAI”) trajectories) the regions will be adjacent certainanatomical regions to better adapt them to perform those functions thanother regions of the implant.

In some embodiments, a distal anchoring region (“DAR” in FIG. 47) of animplant (e.g. composite implant) may have a length from 15 mm to 40 mm,such as from 15 mm to 35 mm, such as from 15 mm to 30 mm, such as from20 mm to 30 mm, such as 25 mm.

In some embodiments, a growth region (e.g. “GR” in FIG. 47) of animplant (e.g. a composite implant) may have a length from 25 mm to 65mm, such as from 30 mm to 60 mm, such as 30 mm to 55 mm, such as 35 mmto 55 mm, such as 45 mm.

In some embodiments, a proximal anchoring region (e.g. “PAR” in FIG. 47)of an implant (e.g. a composite implant) may be from 3 mm to 20 mm, suchas 5 mm to 15 mm.

In some embodiments, an overall screw length of the implant (such as acomposite implant), which may a combination of DAR, GR, and PAR, in someembodiments, may be from 60 mm-100 mm, such as 65 mm to 95 mm, such as70 mm, to 90 mm, such as 75 mm to 85 mm, such as 80 mm.

In some embodiments, an overall implant length (such as a compositeimplant), which may a combination of DAR, GR, optional PAR, and proximalcoupling region 4760, may be from 65 mm-110 mm, such as 70 mm to 105 mm,such as 75 mm, to 100 mm, such as 80 mm to 95 mm, such as 85 mm.

With reference to FIG. 47, in methods of use, distal anchoring regionDAR may be implanted in an ilium. Growth region GR may be implantedacross an SI joint, and proximal anchoring region PAR may be implantedin a sacrum. A tulip can be coupled to proximal coupling region 4760,and a stabilizing rod can be secured to the tulip. More than onecomposite implant can be positioned across an SI joint in thetrajectories described herein. One or more stabilizing rods may besecured to any number of implanted composite implants herein.

One aspect of this disclosure is related to bone stabilizing implantthat includes one or more deployable members, the one or more deployablemembers having non-deployed configurations and a deployed configuration.FIGS. 48A-48H illustrate an exemplary embodiment of a bone stabilizingimplant that includes one or more deployable members. FIG. 48A is aperspective view of exemplary bone stabilizing implant 4800 including anelongate implant body 4802 and a plurality of deployable members 4804and 4804′ (only some or each are labeled for clarity). The deployablemembers in this embodiment may be referred to as protrusions or fins,and in FIG. 48A are shown in their deployed configurations. If the term“fin” or “fins” is used in the text or figures, the more generalizedterm “deployable member(s)” is understood to apply as well. FIG. 48Bshows deployable members in deployed configurations/positions, whileFIG. 48C shows the deployable members in non-deployed (e.g., recessed)configurations/positions.

FIG. 48D shows a side view of implant 4800. FIG. 48D illustrates threadsof the elongate implant body 4802 pass through openings between adjacentdeployable members 4804. The threads thereby provide a mechanical stopfor the deployable members 4804 by limiting upward travel, and preventthe opening from bowing under load. The deployable members are deployed.

FIG. 48E shows a perspective sectional view of the implant in the regionshown in FIG. 48D. FIG. 48E shows internal deployment member 4810, whichcan be part of the implant or a deployment tool that is not part of theimplant and is removed from the patient following the deployment step.The internal deployment member can be function as a camming member, andwhen rotated has camming surfaces that urge the deployable member(s)radially outward to their deployed positions/configurations. Theinternal deployment member 4810 may stay in place with the implant, andmay help the deployable members stay in their deployed configurations.The openings 4820 in the elongate body 4802 (through which thedeployable members extend), one of which is labeled in FIG. 48G can betapered to limit the play between the deployable members and theelongate implant body 4802. In some embodiments the internal deploymentmember 4810 may be made titanium (for example without limitation), andmay be manufactured with subtractive manufacturing techniques. Thedeployable member(s) may in some embodiments be titanium (for examplewithout limitation), and can be manufactured using subtractivemanufacturing techniques.

FIG. 48F shows an exemplary exploded view of implant 4800. Implant 4800includes elongate body or sleeve 4802, which is threaded as shown andincludes a plurality of sets of linear openings 4820 separated by thethreads. The implant includes deployable or expandable members 4804,which in this embodiment are each coupled to a spine from which each ofthe deployable members 4804 extends, as shown in FIG. 48F. The spine anddeployable members may be integrally formed from the same material ornot. The linear spine and deployable members are disposed within thebody 4802, and urged radially outward by actuation member 4810, detailsof which are shown in FIG. 48E. Threaded tip 4820 can be coupled to thedistal end region of body 4802 using a variety of coupling techniques.

FIGS. 48G and 48H illustrate perspective sectional views of implant 4800in non-deployed (FIG. 48G) and deployed (FIG. 48H) configurations.Additional details are shown in other figures within FIG. 48A-48F.

Exemplary methods of implanting implant 4800 can include one or more offollowing steps, and may not necessary be in the order that follows.During implant insertion, the deployable members 4804, 4804′, 4804″ arein non-deployed (e.g. recessed) positions relative to implant body 4802.The implant can be threaded into bone similar to a screw. After theimplant is located in a target location, the deployable members can bedeployed by actuating the inner actuation member, such as by rotatingthe inner actuating member, which may include one or more cammingsurfaces. The deployed member (e.g., 4804) are configured, oncedeployed, to aid in preventing joint rotation, thereby increasing thestability of the joint. The elongate body 4804, which can include anyfeatures of any sleeve herein, can include one or more growth features(e.g., fenestrations, lattice sections) to facilitate one or more ofbony on-growth, in-growth, or through-growth.

Implant 4800 is an example of an implant with an elongate implant bodythat includes one or more threads, optionally a plurality of regionshaving different number of leads.

Implant 4800 is an example of an implant with an elongate body (e.g.4802) that includes a plurality of rows of openings (optionally linearrows), each of the rows including a plurality of openings separated by aportion of the elongate implant body.

Implant 4800 is an example of an implant with an elongate implant bodythat separates a plurality of openings, wherein the separating portionincludes one or more threads.

Implant 4800 is an example of an implant with deployable members,wherein any of the deployable members include a plurality of protrusionsextending from a spine, the protrusions extending further radiallyoutward than the spine, and optionally the protrusions formed integrallywith the spine.

Implant 4800 is an example of an implant with one or more deployablemembers that are positioned relative to an elongate implant body 4802such that they are deployed upon actuation of an internal deploymentmember.

Implant 4800 is an example of an implant wherein an internal deploymentmember comprises a plurality of radially protruding camming surfacesthat when rotated cause one or more deployable members to move radiallyoutward.

Implant 4800 is an example of an implant with one or more threads on anelongate implant body, wherein the threads provide a mechanical radialstop to one or more deployable members, optionally preventing theopening(s) from bowing under load.

Implant 4800 is an example of an implant with an implant body withopenings that can be tapered to limit play between the elongate implantbody and the one or more deployable members.

Implant 4800 is an example of an implant with an elongate implant bodythat can have one or more porous surfaces.

Implant 4800 is an example of an implant with a plurality of deployablemembers that can be actuated and deployed by an inner actuatable member.

Any of the composite implants herein can include a volume defined by aninner surface of the sleeve and an outer surface of the shank. That is,a gap can exist between the outer surface of the shank and the innersurface of the sleeve. The volume can facilitate bony ingrowth.

As set forth above, when the composite implants herein are advanced viaa posterior sacral alar-iliac (“SAI”) trajectory and disposed across anSI joint, it can be advantageous when certain regions of the implant areadjacent certain bone or tissue once fully implanted. As set forthabove, the distal region of the implant is generally configured to beable to better anchor into relatively denser cortical bone, such as witha dual threaded distal region. With some of the composite implants above(e.g. FIG. 34A), the sleeve is tapered in a distal region and includes adual threaded region. A central region of the sleeve proximal to thedistal tapered region (which can be part of an implant growth region)may be single thread (e.g. FIG. 34A), and can have one or more growthfeatures configured to better facilitate at least one of bony on-growth,in-growth, or through-growth than the distal anchoring region. Forexample, in several examples herein (e.g. FIGS. 34-47), the centralgrowth region includes at least one of one or more fenestrations or oneor more lattice sections, examples of each are provided herein. Somesleeves herein can optionally also include a dual-lead proximal endregion, such as in FIG. 31, 33C, 34A, 36A, 41A, 44A, which can betterconfigure the composite implant proximal region to anchor into the moredense cortex of the sacrum. In some embodiments, the sleeve may have acentral region with a single lead, a proximal region with a multi-lead(e.g. dual), and optionally a distal region that is multi-lead (e.g.dual lead).

In some methods of use, the implants herein (e.g. the compositeimplants) as delivered with a posterior sacral alar-iliac (“SAI”)trajectory. Without intending to be limiting, there can be benefits toimplanting any of the composite implants herein such that at least 15 mmof the implant extends distal to the SI joint in the final implantedposition. In some methods of use the implants extend at least 15 mm-20mm beyond the SI joint. The distal anchoring region thus can havelengths that facilitate a distal anchoring region of the implantextending at least 15 mm beyond the joint. This can help ensure theimplant distal anchoring region extends into the dense cortical iliumbone and helps anchor the implant.

Any of the sleeves herein include an inner lumen, the inner lumen sizedand configured to receive at least a portion of an inner member (e.g.inner shank).

Variations and modifications of the devices and methods disclosed hereinwill be readily apparent to persons skilled in the art. As such, itshould be understood that the foregoing detailed description and theaccompanying illustrations, are made for purposes of clarity andunderstanding, and are not intended to limit the scope of the invention,which is defined by the claims appended hereto. Any feature described inany one embodiment described herein can be combined with any otherfeature of any of the other embodiment whether preferred or not.

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art and areto be included within the spirit and purview of this application andscope of the appended claims. All publications, patents, and patentapplications cited herein are hereby incorporated by reference for allpurposes.

What is claimed is:
 1. A composite implant for stabilizing a sacroiliac(“SI”) joint, comprising: a monolithic inner shank including one or morethreads in a distal threaded region; and an outer sleeve comprising oneor more outer threads that are in the same direction as the one or morethreads in the distal threaded region of the inner shank, and aplurality of surface growth features that are sized and configured tofacilitate at least one of bony on-growth, in-growth, or through-growth,the outer sleeve disposed about a central portion of the monolithicinner shank with at least a portion of the outer sleeve coupled to theinner shank, the composite implant further comprising a distal anchoringregion that includes the distal threaded region of the monolithic innershank, and a growth region that includes the plurality of surface growthfeatures and that is proximal to the distal anchoring region, the distalanchoring region better adapted to anchor into iliac bone than thegrowth region, and the plurality of surface growth features betterconfigured to facilitate the at least one of bony on-growth, in-growth,or through-growth than the anchoring region.
 2. The composite implant ofclaim 1, further comprising a multi-lead threaded distal region thatincludes the distal threaded region of the inner shank, a single-leadthreaded central region that is proximal to the multi-lead threadeddistal region and that comprises one of the outer sleeve one or moreouter threads, and multi-lead threaded proximal region proximal to thesingle-lead threaded central region.
 3. The composite implant of claim2, wherein the outer sleeve comprises the multi-lead threaded proximalregion.
 4. The composite implant of claim 2, wherein the monolithicinner shank comprises the multi-lead threaded proximal region.
 5. Thecomposite implant of claim 1, wherein in a region between an outersleeve distal end and an outer sleeve proximal end, the inner shank ismore resistant to fatigue than the sleeve.
 6. The composite implant ofclaim 1, wherein the inner shank is made of one or more of titanium orstainless steel.
 7. The composite implant of claim 6, wherein the outersleeve is a 3D printed outer sleeve.
 8. The composite implant of claim1, wherein the one or more outer threads of the outer sleeve comprise adual-lead thread region and a single-lead thread region.
 9. Thecomposite implant of claim 1, wherein the plurality of surface growthfeatures comprises a plurality of fenestrations extending through theouter sleeve.
 10. The composite implant of claim 9, wherein at leasthalf of the plurality of fenestrations are disposed axially in betweenone or more outer sleeve thread crests.
 11. The composite implant ofclaim 9, wherein each of the plurality of fenestrations are disposedaxially in between one or more outer sleeve thread crests.
 12. Thecomposite implant of claim 9, wherein a subset of the plurality offenestrations are disposed in an at least partial helical configuration.13. The composite implant of claim 12, wherein a second subset of theplurality of fenestrations are disposed in an at least partial helicalconfiguration.
 14. The composite implant of claim 9, wherein one or moreof the plurality of fenestrations are tapered and have an outerdimension that is larger than an inner dimension.
 15. The compositeimplant of claim 1, wherein the plurality of surface growth featuresinclude a plurality of lattice sections extending through at least anouter surface of the outer sleeve wherein each of the plurality oflattice section includes pores having dimensions smaller than each of aplurality of outer sleeve fenestrations, wherein a set of latticesections are disposed in a partial helical configuration along thecomposite implant.
 16. The composite implant of claim 15, wherein afirst group of the plurality of lattice sections extend all the waythrough a thickness of the outer sleeve, and a second group of theplurality of lattice sections only extend through an outer surface ofthe outer sleeve and not all the way through the thickness of thesleeve.
 17. The composite implant of claim 1, wherein the plurality ofsurface growth features comprises a plurality of lattice sections, atleast a subset of the plurality of lattice sections do not extend allthe way through a thickness of the outer sleeve.
 18. The compositeimplant of claim 17, wherein the subset of the plurality of latticesections are disposed inside of a sleeve flute.
 19. The compositeimplant of claim 17, wherein a second subset of the plurality of latticesections extend all the way through the outer sleeve.
 20. The compositeimplant of claim 17, wherein the plurality of lattice sections aredisposed axially adjacent at least one sleeve thread.
 21. The compositeimplant of claim 17, wherein a subset of the plurality of latticesections are disposed in an at least partial helical configuration. 22.The composite implant of claim 1, wherein the inner shank is stifferthan the outer sleeve.
 23. The composite implant of claim 1, wherein theouter sleeve is not interfaced with the inner shank in the centralportion.
 24. A composite implant for stabilizing a sacroiliac (“SI”)joint, comprising: a monolithic inner shank including one or morethreads in a distal threaded region; and an outer sleeve comprising oneor more outer threads that are in the same direction as the one or morethreads in the distal threaded region of the inner shank, and aplurality of surface growth features that are sized and configured tofacilitate at least one of bony on-growth, in-growth, or through-growth,the outer sleeve disposed about a central portion of the monolithicinner shank with at least a portion of the outer sleeve coupled to theinner shank.
 25. The composite implant of claim 24, further comprising amulti-lead threaded distal region that includes the distal threadedregion of the inner shank, a single-lead threaded central region that isproximal to the multi-lead threaded distal region and that comprises oneof the outer sleeve one or more outer threads, and multi-lead threadedproximal region proximal to the single-lead threaded central region. 26.The composite implant of claim 25, wherein the outer sleeve comprisesthe multi-lead threaded proximal region.
 27. The composite implant ofclaim 25, wherein the monolithic inner shank comprises the multi-leadthreaded proximal region.
 28. The composite implant of claim 24, whereinin a region between an outer sleeve distal end and an outer sleeveproximal end, the inner shank is more resistant to fatigue than thesleeve.
 29. The composite implant of claim 24, wherein the inner shankis made of one or more of titanium or stainless steel.
 30. The compositeimplant of claim 29, wherein the outer sleeve is a 3D printed outersleeve.
 31. The composite implant of claim 24, wherein the one or moreouter threads of the outer sleeve comprise a dual-lead thread region anda single-lead thread region.
 32. The composite implant of claim 24,wherein the plurality of surface growth features comprises a pluralityof fenestrations extending through the outer sleeve.
 33. The compositeimplant of claim 32, wherein at least half of the plurality offenestrations are disposed axially in between one or more outer sleevethread crests.
 34. The composite implant of claim 32, wherein each ofthe plurality of fenestrations are disposed axially in between one ormore outer sleeve thread crests.
 35. The composite implant of claim 32,wherein a subset of the plurality of fenestrations are disposed in an atleast partial helical configuration.
 36. The composite implant of claim35, wherein a second subset of the plurality of fenestrations aredisposed in an at least partial helical configuration.
 37. The compositeimplant of claim 32, wherein one or more of the plurality offenestrations are tapered and have an outer dimension that is largerthan an inner dimension.
 38. The composite implant of claim 24, whereinthe plurality of surface growth features include a plurality of latticesections extending through at least an outer surface of the outer sleevewherein each of the plurality of lattice section includes pores havingdimensions smaller than each of a plurality of outer sleevefenestrations, wherein a set of lattice sections are disposed in apartial helical configuration along the composite implant.
 39. Thecomposite implant of claim 38, wherein a first group of the plurality oflattice sections extend all the way through a thickness of the outersleeve, and a second group of the plurality of lattice sections onlyextend through an outer surface of the outer sleeve and not all the waythrough the thickness of the sleeve.
 40. The composite implant of claim24, wherein the plurality of surface growth features comprises aplurality of lattice sections, at least a subset of the plurality oflattice sections do not extend all the way through a thickness of theouter sleeve.
 41. The composite implant of claim 40, wherein the subsetof the plurality of lattice sections are disposed inside of a sleeveflute.
 42. The composite implant of claim 40, wherein a second subset ofthe plurality of lattice sections extend all the way through the outersleeve.
 43. The composite implant of claim 40, wherein the plurality oflattice sections are disposed axially adjacent at least one sleevethread.
 44. The composite implant of claim 40, wherein a subset of theplurality of lattice sections are disposed in an at least partialhelical configuration.
 45. The composite implant of claim 24, whereinthe inner shank is stiffer than the outer sleeve.
 46. The compositeimplant of claim 24, wherein the outer sleeve is not interfaced with theinner shank in the central portion.